1968 lines
96 KiB
Plaintext
1968 lines
96 KiB
Plaintext
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The Unix Hardware Buyer HOWTO
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Eric Raymond
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<esr@thyrsus.com>
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Revision History
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Revision 4.2 2010-04-11 Revised by: esr
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DVD region-locking firmware is no longer an issue,
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Revision 4.1 2009-07-01 Revised by: esr
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DTX failed. Finally deprecate SCSI. 32-bit is dead. Avoiding the
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printer-consumables trap. Invasion of the netbooks.
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Revision 4.0 2007-11-02 Revised by: esr
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Major revisions by Jonathan Marsden on SATA, bus standards, DVDs and
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other topics, followed by a cleanup pass from me.
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Revision 3.3 2007-18-13 Revised by: esr
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Updated for 2007 conditions. CRTs are dead. BTX is dead. CD-ROMs are
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competely generic now. USB modems are recommended.
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Revision 3.2 2004-10-28 Revised by: esr
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Fix and remove bad links.
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Revision 3.1 2004-08-03 Revised by: esr
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Sound cards don't matter any more.
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Revision 3.0 2004-02-21 Revised by: esr
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Power-protection stuff moved to UPS HOWTO. DIMM memory is gone. Tape
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drives don't make sense any more. Lots of the theory from my
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"Ultimate Linux Box" articles now lives here.
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Revision 2.4 2003-02-22 Revised by: esr
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URL fixes.
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Revision 2.3 2002-08-06 Revised by: esr
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Buying at the low end isn't a lose anymore. I recommend Athlons.
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Nuked the section on video standards, EDID takes care of all that
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now. Also removed the section on older memory types. And keyboards,
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as the "ergonomic" ones all vanished along with the 1990s
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carpal-tunnel scare.
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Revision 2.2 2002-08-05 Revised by: esr
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New section on DVD drives.
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Revision 2.1 2002-07-08 Revised by: esr
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Corrected Kingston URL. Various small updates for the last year. This
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HOWTO is much more stable than it used to be.
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Revision 2.0 2001-08-09 Revised by: esr
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Major update. Revisions based on Ultimate Linux Box experience.
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Caches are on-chip now. DDS4 tape drives are here. 486 machines, CD
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caddies, and most non-DDS backup technologies are gone.
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Revision 1.1 2001-06-13 Revised by: esr
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Mid-2001 update.
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Revision 1.0 2001-02-06 Revised by: esr
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Initial revision; but see the history in the introduction.
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This is your one-stop resource for information about how to buy and
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configure generic PC hardware for cheap, powerful Unix systems.
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________________________________________________________________
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Table of Contents
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1. Introduction
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1.1. Purpose of this document
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1.2. New versions of this document
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1.3. Feedback and corrections
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1.4. Related resources
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2. Overview of the Market
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3. Buying the Basics
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3.1. Things to Not Care About
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3.2. How To Pick Your Processor
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3.3. One Disk or Two?
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3.4. Getting Down to Cases
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3.5. Power Supplies and Fans
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3.6. Motherboards
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3.7. Monitor and Video
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3.8. DVD Drives
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3.9. Sound Cards and Speakers
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3.10. Modems
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3.11. Printers
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3.12. Power Protection
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3.13. Radio Frequency Interference
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4. What To Optimize
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4.1. First, add more memory
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4.2. Bus and Disk speeds
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4.3. Optimizing your disk subsystem
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4.4. Tuning Your I/O Subsystem
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5. But What If I'm Economizing?
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6. Noise Control and Heat Dissipation
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7. Special Considerations When Buying Laptops and Netbboks
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8. How to Buy
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8.1. When to Buy
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8.2. Where to Buy
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8.3. Computer Fairs
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8.4. Mail Order
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8.5. Computer Superstores
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8.6. Other Buying Tips
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9. Questions You Should Always Ask Your Vendor
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9.1. Minimum Warranty Provisions
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9.2. Documentation
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9.3. A System Quality Checklist
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10. Things to Check when Buying
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10.1. Tricks and Traps in Warranties
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10.2. Special Questions to Ask Web/Mail-Order Vendors Before
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Buying
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10.3. Payment Method
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10.4. Which Clone Vendors to Talk To
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11. After You Take Delivery
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12. Software to go with your hardware
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13. Other Resources on Building Linux PCs
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1. Introduction
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1.1. Purpose of this document
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The purpose of this document is to give you the background
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information you need to be a savvy buyer of Intel hardware for
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running Unix. It is aimed especially at hackers and others with the
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technical skills and confidence to go to the Internet/mail-order
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channel, but contains plenty of useful advice for people buying
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store-front retail.
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This document is maintained and periodically updated as a service to
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the net by Eric S. Raymond, who began it for the very best
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self-interested reason that he was in the market and didn't believe
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in plonking down several grand without doing his homework first (no,
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I don't get paid for this, though I have had a bunch of free software
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and hardware dumped on me as a result of it!). Corrections, updates,
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and all pertinent information are welcomed at
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[mailto:esr@snark.thyrsus.com] esr@snark.thyrsus.com. The editorial
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<20>we' reflects the generous contributions of many savvy Internetters.
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If you email me questions that address gaps in the FAQ material, you
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will probably get a reply that says "Sorry, everything I know about
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this topic is in the HOWTO". If you find out the answer to such a
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question, please share it with me for the HOWTO, so everyone can
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benefit.
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If you end up buying something based on information from this HOWTO,
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please do yourself and the net a favor; make a point of telling the
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vendor "The HOWTO sent me" or some equivalent. If we can show vendors
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that this HOWTO influences a lot of purchasing decisions, we get
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leverage to change some things that need changing.
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Note that in December 1996 I published an introductory article on
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building and tuning Linux systems summarizing much of the material in
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this HOWTO. It's available here. In 2001 I published an article on
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building the Ultimate Linux Box.
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This Buyer's Guide actually dates back to 1992, when it was known as
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the "PC-Clone Unix Hardware Buyer's Guide"; this was before Linux
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took over my world :-). Before that, portions of it were part of a
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Unix Buyer's Guide that I maintained back in the 1980s on USENET.
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It may be a matter of historical interest that the page count of this
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guide peaked in mid-2001 and has been declining since. Video, sound,
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and other functions are migrating onto motherboards. Several bus
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types have disappeared, as have all the old-school backup
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technologies that couldn't scale up to match disk capacities, Spec
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sheets are getting simpler. Accordingly, there are parts that used to
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have whole sections to hemselves that I barely even write about
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anymore -- mice, floppy disks, CD-ROM drives, and keyboards, for
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example, are utterly generic now,
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Another consequence of the technology stabilizing is also that I'm
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updating this guide less often than I used to. Years can now go by
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without the PC market changing in any fundamental way.
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In retrospect, the success of the ATX standard for motherboards in
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1998-1999 was probably the turning point. The PC industry has become
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sufficiently commoditized that your choices are now getting simpler
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rather than more complicated. This is a Good Thing.
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________________________________________________________________
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1.2. New versions of this document
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New versions of the Unix Hardware Buyer HOWTO will be periodically be
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uploaded to various Linux WWW and FTP sites, including the LDP home
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page.
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You can view the latest version of this on the World Wide Web via the
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URL [http://www.tldp.org/HOWTO/Unix-Hardware-Buyer-HOWTO/]
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http://www.tldp.org/HOWTO/Unix-Hardware-Buyer-HOWTO/.
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________________________________________________________________
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1.3. Feedback and corrections
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If you have questions or comments about this document, please feel
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free to mail Eric S. Raymond, at [mailto:esr@thyrsus.com]
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esr@thyrsus.com. I welcome any suggestions or criticisms. If you find
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a mistake with this document, please let me know so I can correct it
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in the next version. Thanks.
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________________________________________________________________
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1.4. Related resources
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You may also want to look at the read the
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[http://www.tldp.org/HOWTO/Hardware-HOWTO.html] Hardware-HOWTO. It
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lists hardware known to be compatible with Linux, and hardware known
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to be incompatible. I've also done a series of articles on The
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Ultimate Linux Box.
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________________________________________________________________
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2. Overview of the Market
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The central fact about PC hardware is that de-facto hardware
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standards have created a commodity market with low entry barriers,
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lots of competitive pressure, and volume high enough to amortize a
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lot of development on the cheap.
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The result is that this hardware gives you lots of bang-per-buck, and
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it's getting both cheaper and better all the time. Furthermore,
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margins are thin enough that vendors have to be lean, hungry, and
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very responsive to the market to survive.
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One good general piece of advice is that you should avoid the
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highest-end new-technology systems (those not yet shipping in
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volume). The problem with the high end is that it usually carries a
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hefty "prestige" price premium, and may be a bit less reliable on
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average because the technology hasn't been through a lot of
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test/improve cycles.
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There used to be a real issue with low-end PCs as well, because there
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used to be a lot of dodgy crap PC components out there going into
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boxes made by vendors trying to save a few cents. That's not really a
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problem anymore. Market pressure has been very effective at raising
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reliability standards for even low-end components as the market has
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matured. It's actually hard to go wrong even buying at the bottom end
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of the market these days.
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I put together the first version of this guide around 1992;
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Unix-capable systems are now ten to twenty times cheaper than they
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were then. At today's prices, building your own system from parts no
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longer makes much sense at all --so this HOWTO is now more oriented
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towards helping you configure a whole system from a single vendor.
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________________________________________________________________
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3. Buying the Basics
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In this section, we cover things to look out for that are more or
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less independent of price-performance tradeoffs, part of your minimum
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system for running Unix.
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Issues like your choice of disk, processor, and I/O bus (where there
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is a significant tradeoff between price and capability) are covered
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in the section on What To Optimize.
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________________________________________________________________
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3.1. Things to Not Care About
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An effect of PC commoditization is that there aren lots of things you
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used to have to worry about that don't matter any more, because the
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market has completely flattened out. We list these here to get them
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out of the way.
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________________________________________________________________
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3.1.1. Bus Wars
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The system bus is what ties all the parts of your machine together.
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This is an area in which progress has simplified your choices a lot.
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There used to be no fewer than four competing bus standards out there
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(ISA, EISA, VESA/VLB, PCI, and PCMCIA). Now there are effectively
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just two --PCI-X on servers, and PCIe for desktop/tower machines.
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Even PCI is now legacy technology, and the PCMCIA bus that seemed so
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important a few years back has been reduced to near-irrelevance by
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Ethernet, USB, and WiFi hardware built onto motherboards. The
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newcomer is PCIe, which is (in late 2007) a `video-card-mostly' bus,
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though it seems to be gaining in popularity for other uses too on
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mainstream desktop motherboards, whereas PCI-X is only found on
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higher end `server' motherboards.
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________________________________________________________________
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3.1.2. Memory
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Judging the memory-controller and cache design used to be one of the
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trickiest parts of evaluating a motherboard, but that stuff is all
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baked into the processor itself now. This removed a large source of
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latency and design variations. It also killed off the plethora of
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different RAM types that used to be out there.
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Today's advice is very simple. Make sure the memory is rated for your
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machine's bus speed, then buy as much as you can afford to stuff in
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your machine.
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Note
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DDR3 RAM is beginning to appear. Right now its extra expense over
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DDR2 is not worth paying, for all but extremely specialized needs. It
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is almost always far more useful to have 4GB of reasonably fast RAM,
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than 2GB of very fast RAM, in your machine.
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For more technical stuff on memory architectures, see The Ultimate
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Memory Guide maintained by Kingston Technologies.
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________________________________________________________________
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3.1.3. Keyboards and Mice
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Keyboards are mostly generic nowadays. One useful piece of advice is
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to not buy any desktop machine with "Internet" buttons on it; this is
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a sure sign of a PC that's an overpriced glitzy toy. Nowadays
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keyboards with a USB connector are the norm, rather than the older
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dedicated connectors; modern open-source Unixes handle these just
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fine.
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Mice and trackballs used to be simple; then, thanks to Microsoft,
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they got complicated. Now they're simple again. Again, USB mice have
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replaced the older PS/2-style dedicated connector. XFree86
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autodetects your mouse when it starts up, so configuration is not a
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big deal any more.
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Some PC vendors, being Windows-oriented, still bundle two-button
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mice. Thus, you may have to buy your own three-button (or two button
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and a scroll wheel) mouse. Ignore the adspeak about dpi and pick a
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mouse or trackball that feels good to your hand.
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Your humble editor really, really likes the Logitech TrackMarble, an
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optical trackball that eliminates the chronic roller-fouling problems
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of the older TrackMan. They're well-supported by X, so any Linux or
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BSD will accept them.
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________________________________________________________________
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3.1.4. Floppy Drives
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There's no longer much to be said about floppy drives. They're cheap,
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they're generic, and the rise of CD-ROM and DVD-ROM drives as a cheap
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distribution medium has made them much less important than formerly.
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You only ever see the 3.5-inch `hard-shell' floppies with 1.44MB
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capacity anymore.
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Bootable CD-ROMs killed off the last use of floppies, which was OS
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installation. So go ahead and settle for cheap Mitsumi and Teac
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floppy drives. There are no `premium' floppy drives anymore. Nobody
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bothers.
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It's possible your system won't even include one. No loss.
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________________________________________________________________
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3.1.5. CD-ROM Drives
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Standard CD-ROMs hold about 650 megabytes of read-only data in a
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format called ISO-9660 (formerly "High Sierra"). All current Unixes
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support these devices. Unix and Linux software is now distributed on
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ISO-9660 CD-ROM, a cheaper and better method than the QIC tapes we
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used to use.
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CD-ROM speed used to be a big deal; vendors advertised 2X, 4X, all
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the way up to 52X. Vendors don't bother any more; the drives are all
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about equivalently fast now.
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There are one or two minor features to watch for. Most CD-ROMS will
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include a headphone jack so you can play audio CDs on them.
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Better-quality ones will also include two RCA jacks for use with
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speakers. Another feature to look for is a drive door or seal that
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protects the drive head from dust.
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Increasingly, DVD-ROM drives (and burners) are replacing CD-ROM
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drives as the default optical drive in PC systems. They have
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significantly larger capacity, and will read (and burn) CD media too.
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The cost difference now is so small that it is usually preferable to
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buy a DVD burner instead of a CD-ROM drive.
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________________________________________________________________
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3.1.6. Backup devices
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It's good to be able to make backups that you can separate from your
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system and store off-site in case of disaster. Until about 2001, tape
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drives still seemed like a good idea for personal systems, but I
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found I seldom used mine. Today, tape drives with high enough
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capacity to image today's huge hard disks are too expensive to make
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sense any more.
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For the money you'd spend on a high-capacity tape drive (over $1000)
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it makes more sense to buy a laptop and a pile of CD-R or DVD-R or
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DVD+R media. Sit the laptop on your house Ethernet when you're not
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traveling, and back up the main machine to it every day, or oftener.
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Between the efficiency of rsync and the speed of 100-megabit
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Ethernet, this will be a lot faster than making a tape. Every once in
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a while, burn a set of backup CD-ROMs or DVDROMs.
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But CD-ROMs aren't reusable; the cost piles up over time. An
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interesting alternative is a small external USB hard drive,
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especially if you can salvage an old laptop drive and put it in a USB
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enclosure. These enclosures are available for about $30; Google for
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"USB HD Enclosure". This is faster than a tape, cheaper and lighter
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than a full laptop. For faster transfer speeds, an enclosure that
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accepts eSATA connections as well as USB helps a lot (assuming your
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PC or notebook has an eSATA connector).
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________________________________________________________________
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3.2. How To Pick Your Processor
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Right now (early 2010), the chips to consider for running Unix are
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the the 64-bit AMD Opteron or its Intel equivalents, especially the
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Core 2 Duo. We're long past the point at which 32-bit chips are
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interesting for new desktop systems, presuming you could even find
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one. AMD and Intel built up a buffer before switching their fabs
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fully to 64-bit chips in 2006, and the 32-bit chips you can still
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find are coming out of warehouses rather than off production lines.
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Brands don't matter much, so don't feel you need to pay Intel's
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premiums if you see an attractive Cyrix, AMD or other chip-clone
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system offered. In the last few years I've been a big fan of the AMD
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line. They used to be faster, cheaper, and better-designed than Intel
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processors; today Intel has clawed back the speed advantage, but AMD
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chips still deliver more performance than you're likely to be able to
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use and do it with lower power dissipation (thus, less noise and
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heat).
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On the other hand, Intel-chip motherboards now have the advantage
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that the on-board graphics chip will give you 3D acceleration with
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fully open-source drivers. This will avoid the problems you would
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otherwise face trying to select a supported graphics card from ATI or
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Nvidia.
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Many CPUs now are multi-core -- that is, they have multiple CPUs on a
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single chip. This is very useful for doing something compute
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intensive (re-encoding video, compressing large archives, etc.) in
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the background and still having a responsive system for other work at
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the same time. At current prices, a dual-core CPU makes good sense
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for most desktop systems. If you are building a server or have
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specialized computing needs you expect to be very CPU-intensive
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quad-core is worth considering, but on a desktop system all the two
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extra cores will usually do is emit heat. Only at the very low end
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(sub US$50 CPUs) do single-core CPUs still make sense on desktop
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machines.
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Mainstream desktop CPUs now use one of two sockets: LGA 775 (Intel)
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and AM2 (AMD). Buying a system that uses one of these stands more
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chance of allowing a useful CPU upgrade to extend its useful life
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than systems using other less common sockets.
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Current CPUs are much faster than those of just a few years ago. As a
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result, unless your needs are highly specialized, spending more than
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about US$200 on a desktop CPU is hard to justify. For most users,
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putting extra budget into more RAM or a faster disk subsystem will
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most likely result in greater benefit.
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________________________________________________________________
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3.3. One Disk or Two?
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I usually build with two disks -- one "system" disk and one "home"
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disk. There are two good reasons to do this that have nothing to do
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with the extra capacity. One of them is the performance advantage of
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being able to interleave commands to different physical spindles that
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we'll explain a bit later in the section on disks. The other is that
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I am quite a bit less likely to lose two disks at once than I am to
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trash a single one.
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Let's suppose you have a fatal disk crash. If you have only one disk,
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goodbye Charlie. If you have two, maybe the crashed one was your
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system disk, in which case you can buy another and mess around with a
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new Linux installation knowing your personal files are safe. Or maybe
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it was your home disk; in that case, you can still run and do
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recovery stuff and basic Net communications until you can buy another
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home disk and restore it from backups (you did keep backups, right?).
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Given today's high capacity drives, another way to use two disks well
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is to set them up as a RAID1 (mirrored) array. This can be done in
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software or with a hardware RAID controller. This way if either of
|
||
the two drives fail, the system will continue to function, no data is
|
||
lost, and upon replacing the failed drive, the array can be rebuilt
|
||
from the remaining working drive. Hard drives are consumable media,
|
||
they do fail, so this approach (as well as good backups) is well
|
||
worth considering.
|
||
|
||
Buy SATA. The older IDE and EIDE buses are now obsolete, and SCSI no
|
||
longer has enough of a cost advantage to justify the premium. In
|
||
fact, SCSI has effectively nerged into SCSI; SATA is SCSI commands
|
||
being shipped over a single-wire data line.
|
||
________________________________________________________________
|
||
|
||
3.4. Getting Down to Cases
|
||
|
||
I used to say that cases are just bent metal, and that it doesn't
|
||
much matter who makes those. Unfortunately, this isn't true any more.
|
||
Processors run so hot these days that fans and airflow are a serious
|
||
concern. They need to be well designed for proper airflow throughout.
|
||
|
||
Look for the following quality features:
|
||
|
||
* Aluminum rather than steel. It's lighter and conducts heat
|
||
better.
|
||
* Unobstructed air intake with at least one fan each (in addition
|
||
to the power supply and processor fans)
|
||
* No sharp metal edges. You don't want to shred your hands when
|
||
you're tinkering with things.
|
||
* There shouldn't be any hot spots (poor air flow).
|
||
* Sturdy card clips. Some poorly-designed cases allow cards to
|
||
wiggle out of their slots under normal vibration.
|
||
* Effective and easy to use mechanisms for attaching hard drives,
|
||
CD-ROM, CD-R/W, DVDs, etc.
|
||
|
||
If you're fussy about RFI (Radio-Frequency Interference), it's worth
|
||
finding out whether the plastic parts of the case have conductive
|
||
coating on the inside; that will cut down emissions significantly,
|
||
but a few cheap cases omit it.
|
||
|
||
Should you buy a desktop or tower case? Our advice is go with tower
|
||
unless you're building a no-expansions personal system and expect to
|
||
be using the floppies a lot. Many vendors charge nothing extra for a
|
||
tower case, and the cost difference will be trivial even if they do.
|
||
What you get for that is less desktop clutter, more and bigger bays
|
||
for expansion, and often (perhaps most importantly) a beefed-up
|
||
power-supply and fan. Putting the box and its fan under a table is
|
||
good for maybe 5db off the effective noise level, too. Airflow is
|
||
also an issue; if the peripheral bays are less cramped, you get
|
||
better cooling. Be prepared to buy extension cables for your keyboard
|
||
and monitor, though; vendors almost never include enough flex.
|
||
|
||
The airflow thing is a good argument for a full- or mid-tower rather
|
||
than the `baby tower' cases some vendors offer. However, smaller
|
||
towers are getting more attractive as boards and devices shrink and
|
||
more functions migrate onto the motherboard. A state of the art
|
||
system, with all 3" disks, 300W power supply, half-size motherboard,
|
||
on-board SATA and 4GB of RAM sockets, and half-sized expansion cards,
|
||
will fit into a baby or midsized tower with ample room for expansion;
|
||
and the whole thing will fit under a desk and make less noise than a
|
||
classic tower.
|
||
|
||
For users with really heavy expandability requirements, rackmount PC
|
||
cases do exist (ask prospective vendors). Typically a rackmount case
|
||
will have pretty much the same functionality as an ordinary PC case.
|
||
But, you can then buy drive racks (complete with power supply), etc.
|
||
to expand into. Also, you can buy passive backplanes with up to 20 or
|
||
so slots. You can either put a CPU card in one of the slots, or
|
||
connect it to an ordinary motherboard through one of the slots.
|
||
|
||
Since USB has taken over most forms of detachable peripheral, a good
|
||
feature to look for in a case is USB ports mounted at the top forward
|
||
edge where it's easy to plug in digital cameras and the like.
|
||
________________________________________________________________
|
||
|
||
3.5. Power Supplies and Fans
|
||
|
||
A lot of people treat power supplies as a commodity, so many
|
||
interchangeable silver bricks. We know better -- cheap power supplies
|
||
go bad, and when they go bad they have a nasty habit of taking out
|
||
the delicate electronics they're feeding. Also, the power supply
|
||
tends to be the noisiest component in your system.
|
||
|
||
Give preference to supplies with a Underwriter's Laboratories rating.
|
||
There's some controversy over optimum wattage level. On the one hand,
|
||
you want enough wattage for expansion. On the other, big supplies are
|
||
noisier, and if you draw too little current for the rating the
|
||
delivered voltage can become unstable. And the expected wattage load
|
||
from peripherals is dropping steadily. On the other hand, processors
|
||
and their cooling fans eat a lot more power than they used to.
|
||
|
||
The choice is generally between 200W and 300W. After some years of
|
||
deprecating 300W-and-up supplies as overkill, I'm now persuaded it's
|
||
time to go back to them; a modern processor can consume 50-75W by
|
||
itself, and for the newer dual-processor board the power supply needs
|
||
to be rated 450W or up.
|
||
|
||
Processors on modern motherboards run hot enough that all vendors
|
||
have gone to embedded temperature sensors and variable-speed
|
||
thermostat-controlled fans, out sheer self-defense (this used to be a
|
||
high-end only feature).
|
||
|
||
To cut noise, look for 120mm fans rather than the old-style 80mm
|
||
muffin fans. These can move the same amount of air per minute
|
||
rotating at a lower tip speed, which means less vortex formation and
|
||
less noise. These are now becoming standard even on cheap white-box
|
||
hardware.
|
||
|
||
In garden-variety tower cases there often isn't enough airflow to
|
||
cool all components effectively with a single fan, even going at full
|
||
speed. And the single fan in the power supply was basically designed
|
||
to cool the power supply, not the components in the case. This is why
|
||
processors and some graphics cards have their own fans now.
|
||
|
||
A few years ago PCs often had two or more case fans in addition to
|
||
the power-supply fan. This made sense in the era of 80mm fans and
|
||
lots of expansion cards obstructing the airflow, but it was noisy.
|
||
Nowadays, with sound and graphics and Ethernet integrated onto
|
||
motherboards, expansion cards are much less common (and processors
|
||
carry their own mini-fans). Thus, today's standard is to mount one
|
||
120mm fan, usually low and forward just beneath the disk-drive stack.
|
||
This is much quieter, like by a factor of three or four.
|
||
|
||
The noise produced by a fan is not just a function of the speed with
|
||
which it turns. It also depends on the nature of the airflow produced
|
||
by the fan blades and the bearings of the rotor. If the blades cause
|
||
lots of turbulent airflow, the fan produces lots of noise. One brand
|
||
of fans that is much more silent than most others even if going at
|
||
full throttle is [http://www.papstplc.com/] Papst.
|
||
________________________________________________________________
|
||
|
||
3.6. Motherboards
|
||
|
||
Provided you exercise a little prudence and stay out of the price
|
||
basement, motherboards and BIOS chips don't vary much in quality.
|
||
There are only six or so major brands of motherboard inside all those
|
||
cases and they're pretty much interchangeable; brand premiums are low
|
||
to nonexistent and cost is strictly tied to maximum speed and bus
|
||
type. There are only four major brands of BIOS chip (AMI, Phoenix,
|
||
Mylex, Award) and not much to choose between 'em but the look of the
|
||
self-test screens (even the "name" vendors use lightly customized
|
||
versions of these). One advantage Unix buyers have is that Unixes are
|
||
built not to rely on the BIOS code (because it can't be used in
|
||
protected mode without more pain than than it's worth). If your BIOS
|
||
will boot properly, you're usually going to be OK.
|
||
|
||
Some good features to look for in a motherboard include:
|
||
|
||
* Gold-plated contacts in the expansion slots and RAM sockets.
|
||
Base-metal contacts tend to grow an oxidation layer which can
|
||
cause intermittent connection faults that look like bad RAM chips
|
||
or boards. (This is why, if your hardware starts flaking out, one
|
||
of the first things to do is jiggle or remove the boards and
|
||
reseat them, and press down on the RAM chips to reseat them as
|
||
well --this may break up the oxidation layer. If this doesn't
|
||
work, rubbing what contacts you can reach with a soft eraser is a
|
||
good fast way to remove the oxidation film. Beware, some hard
|
||
erasers, including many pencil erasers, can strip off the
|
||
plating, too!)
|
||
* The board should be speed-rated as high as your processor, of
|
||
course. It's good if it's rated higher, so upgrade to a faster
|
||
processor is just a matter of dropping in the chip and a new
|
||
crystal.
|
||
|
||
(I used to have "Voltage, temperature and fan speed monitoring
|
||
hardware." on this list. But processors run so hot nowadays that all
|
||
current motherboards have it.)
|
||
|
||
The dominant form factor is still ATX. Intel tried to replace it with
|
||
a new standard called BTX in late 2004-2005, but failed; the proposal
|
||
was effectively withdrawn in 2006. In January 2007 AMD announced a
|
||
[http://www.dtxpc.org/] DTX specification for small-form-factor PCs;
|
||
it seems also to have sunk without trace.
|
||
________________________________________________________________
|
||
|
||
3.7. Monitor and Video
|
||
|
||
The largest user-visible change since the last major update of this
|
||
guide is that the CRT (cathode-ray tube) is dead. The manufacturers
|
||
shut down their production lines in late 2004; the remaining CRTs out
|
||
there are old stock that's been sitting in warehouses. The only
|
||
reason to buy one since then has been to get high-end resolution at a
|
||
price lower than the insanely expensive high-end flatscreens; with
|
||
1920x1440 flatscreens having become generally available at reasonable
|
||
prices even that reason is gone. It's all flatscreens now, baby.
|
||
|
||
On flatscreens, only two statistics matter; pixel size and response
|
||
time. The biggest functional drawback of flatscreens relative to CRTs
|
||
is that they refresh more slowly, because cheical reactions in a
|
||
flatscreen pixel take longer than remodulating a flying electron
|
||
beam. You'll never notice this during ordinary desktop use, but it
|
||
can cause streakiness and artifacts when you're playing games or
|
||
viewing movies. If you're going to do that a lot, the price premium
|
||
for a flatscreen with better response time may be worth it.
|
||
|
||
Next, buy your card (if you have to; see next paragraph). This used
|
||
to be complicated, with issues like matching the video bandwidths of
|
||
the card and the CRT, and the amount of display memory. Now (unless
|
||
you are a gamer or have similarly extreme 3D acceleration
|
||
requirements) it's simple; all cards have enough display memory for
|
||
every resolution in use, and the issues are software (does it have an
|
||
open-source driver, and do you care?)
|
||
|
||
It's actually fairly likely you'll never buy a video card again. Very
|
||
capable graphics chips are routinely integrated onto motherboards
|
||
now; unless you're a gamer or somebody else who absolutely must have
|
||
the latest wheeze in 3D acceleration, they'll be good enough. Even
|
||
this is not a stable situation, as 3D acceleration is commoditizing
|
||
too.
|
||
|
||
I used to carry a lot of material on different video standards,
|
||
interlacing, and flicker. That stuff is all obsolete now.
|
||
|
||
Here's what to look for on the monitor spec sheet:
|
||
|
||
* Screen size and format. Usually measured in diagonal inches. Most
|
||
displays are now in a "widescreen" format (16:10 ratio of
|
||
width:height) rather than the older 5:4 or 4:3 ratios common for
|
||
CRTs and older flat panel screens. A "19 inch" widescreen monitor
|
||
generally has considerably fewer pixels than a "19 inch" 5:4
|
||
ratio one. Unfortunately, this chane is bad for pogrammers, as it
|
||
tends to lose us the vertical pixel resolution we want for editor
|
||
windows.
|
||
* Screen resolution. 1280x1024 is now low end on the desktop.
|
||
Seventeen inch 1280x1024 screens are the bargain basement now,
|
||
many manufacturers have already switched production to 19 inch
|
||
widescreen 1440x900 screens instead. The cost difference between
|
||
such screens and 20 inch 1680x1050 screens is very small, making
|
||
the 20 inch screens a better choice unless funds (or desktop
|
||
space!) are very tight.
|
||
* 5ms or lower response time. 3ms is better. There is some
|
||
marketing-speak going on in the way the response time is
|
||
specified (grey to gray rather than black to white) but since
|
||
most manufacturers do it this way these times are usually
|
||
comparable between different manufacturers screens.
|
||
* Does it have a tilt-and-swivel base? Adequate controls, including
|
||
both horizontal and vertical size and horizontal and vertical
|
||
centering? A color-temperature control is a plus; the last is
|
||
particularly important if you compose graphics on screen for
|
||
hardcopy from a printer.
|
||
|
||
If you can, buy your monitor from someplace that will let you see the
|
||
same monitor (the very unit you will walk out the door with, not a
|
||
different or `demo' unit of the same model) that will be on your
|
||
system. There's significant quality variation (even in "premium"
|
||
monitor brands) even among monitors of the same make and model.
|
||
________________________________________________________________
|
||
|
||
3.8. DVD Drives
|
||
|
||
DVD drives have two main uses in computer systems: playback of video
|
||
DVDs, and use for data storage (either installation media or backups,
|
||
or even as a primary drive in a few specialized systems).
|
||
|
||
DVD video playback used to be problematic on Unix due to various
|
||
stupid copy-protection schemes in firmware, but they have long since
|
||
been cracked. These days, any SATA DVD will do fine.
|
||
|
||
DVD burners (drives that can read and write CDROM media as well as
|
||
several kinds of DVD media) are now low cost and useful. The SATA
|
||
interface has taken over here, too. Linux and most current PC
|
||
Unix-like systems will work fine with either interface, which is good
|
||
as most PCs now ship with one.
|
||
________________________________________________________________
|
||
|
||
3.9. Sound Cards and Speakers
|
||
|
||
You can't buy a really bad sound card any more. Even low-end sound
|
||
cards or the sound chips embedded in a lot of PC motherboards these
|
||
days support support all these features:
|
||
|
||
* 16-bit sampling (for 65536 dynamic levels rather than 256).
|
||
* Mono and stereo support.
|
||
* Full-duplex mode.
|
||
* Sampling rate of 44.1KHz (CD-quality).
|
||
* MIDI interface via a standard 15-pin D-shell connector.
|
||
* RCA output jacks for headphones or speakers.
|
||
* A microphone jack for sound input.
|
||
|
||
If you are interested in multi-track digital recording, two
|
||
particularly good choices are the M-Audio Delta, or RME Hammerfall
|
||
series of cards. Decent (and lower cost!) two-channel cards for more
|
||
normal use are those using the ICE1712 (Envy24) and ICE1724
|
||
(Envy24HT) audio chips. For normal users, though, the on-motherboard
|
||
chips will work fine.
|
||
|
||
A rather comprehensive list of sound cards and chips supported by the
|
||
ALSA project, which is the main way sound cards are supported under
|
||
Linux, can be found at ALSA Sound Card Matrix.
|
||
|
||
In speakers, look for a magnetically-shielded enclosure with volume,
|
||
bass and treble controls. Some speakers run off the card's 4-watt
|
||
signal; others are "self-powered", using batteries or a separate
|
||
power supply. Your major buying choice is which one of these options
|
||
to pursue. Usually you'll want separately-powered speakers. If
|
||
appropriate for your listening habits, a pair of decent headphones
|
||
will get you better quality sound for the money compared to speakers.
|
||
|
||
One final, important tip: that audio cable from your CD-ROM back to
|
||
the sound card is used only when you play audio CD-ROMs through your
|
||
speakers. Software-generated sound goes through the system bus, so
|
||
you can play games with sound even if your sound board or motherboard
|
||
won't accept the audio cable connector.
|
||
________________________________________________________________
|
||
|
||
3.10. Modems
|
||
|
||
Demand for (dialup telephone) modems is dropping as more and more
|
||
people get broadband Internet through DSL and cable. This section
|
||
still has as much detail as it does only because (a) there are people
|
||
out beyond the exurbs who can't get broadband, and (b) there are one
|
||
or two remaining traps for the unwary.
|
||
|
||
The modem market has stabilized and standardized. If you can spend
|
||
$59, get a U.S. Robotics V.92 USB external. You can then know that
|
||
you've got the best and skip the rest of this section. If you really
|
||
must economize, spend $39 for the internal-card version (but you'll
|
||
probably regret the $20 first time you have to do diagnostics).
|
||
|
||
Note
|
||
|
||
If you live somewhere with really bad telephone lines, the U.S.
|
||
Robotics V.92 Business Modem may be truly "the best" for your needs,
|
||
though it is about four times the price of the U.S. Robotics V.92 USB
|
||
external, which is marketed for home use. See the
|
||
[http://www.usrobotics.com] U.S. Robotics web site for current
|
||
product numbers and more detailed specifications.
|
||
|
||
The modem market is like consumer electronics (and unlike the
|
||
computer market as a whole) in that price is a very poor predictor of
|
||
performance. For ordinary file transfers, some $50 modems are better
|
||
than some $150 modems. Paying top dollar mainly buys you better
|
||
tolerance of poor connections and better performance at heavy-duty
|
||
bi-directional transfers (such as you would generate, for exmaple,
|
||
using SLIP or PPP over a leased line to an Internet provider).
|
||
|
||
In today's market all modems do a nominal 56kbps --V.90 and V.92 plus
|
||
V.29 or V.17 fax transmission and reception (over plain old phone
|
||
lines you won't get more than 53K of that). You don't see much in the
|
||
way of slow/cheap to fast/expensive product ranges within a single
|
||
brand, because competition is fierce and for many modem board designs
|
||
(those featuring DSP (Digital Signal Processor) chips run by a
|
||
program in ROM) adding a new protocol is basically a software change.
|
||
________________________________________________________________
|
||
|
||
3.10.1. Internal vs. External
|
||
|
||
Most modems come in two packagings: internal, designed to fit in a PC
|
||
card slot, and external, with its own case, power supply, and
|
||
front-panel lights. Typically you'll pay $20 to $30 more for an
|
||
external modem than you will for the internal equivalent. You'll also
|
||
need a serial or USB port to connect your external modem to.
|
||
|
||
Pay that premium -- being able to see the blinkenlights on the
|
||
external ones will help you understand and recover from pathological
|
||
situations. For example, if your Unix system is prone to
|
||
"screaming-tty" syndrome, you'll quickly learn to recognize the
|
||
pattern of flickers that goes with it. Punch the hangup/reset button
|
||
on an external modem and you're done -- whereas with an internal
|
||
modem, you have to go root and flounder around killing processes and
|
||
maybe cold-boot the machine just to reset the card.
|
||
|
||
See Rick's Rants for extended discussion of this point.
|
||
________________________________________________________________
|
||
|
||
3.10.2. Pitfalls to Avoid
|
||
|
||
Don't buy a serial (RS232C) modem. This used to be the only kind
|
||
there was, but they were always a bitch to configure and
|
||
troubleshoot. Go USB instead; the sanity you save may be your own.
|
||
|
||
If the abbreviation "RPI" occurs anywhere on the box, don't even
|
||
consider buying the modem. RPI (Rockwell Protocol Interface) is a
|
||
proprietary "standard" that allows modem makers to save a few bucks
|
||
at your expense by using a cheap-jack Rockwell chipset that doesn't
|
||
do error correction. Instead, it hands the job off to a modem driver
|
||
which (on a Unix machine) you will not have.
|
||
|
||
Also avoid anything called a "Windows Modem" or "WinModem", "HCF", or
|
||
"HSP"; these lobotomized pieces of crap require a Windows DLL to run.
|
||
They will eat up to 25% of your processor clocks during transfers,
|
||
and hog high-priority interrupts (causing your machine to stall under
|
||
Windows even if your processor still has spare cycles).
|
||
|
||
A good way to avoid falling into the WinModem trap is to look for the
|
||
designation "OEM modem". This is apparently the new industry-speak
|
||
for a modem with an on-board harware DSP. Occasionally you'll see
|
||
these called "gaming modems".
|
||
________________________________________________________________
|
||
|
||
3.10.3. Fax Modems
|
||
|
||
Many modems come with bundled Windows fax software that is at best
|
||
useless under Unix, and at worst a software kluge to cover inadequate
|
||
hardware. Avoid these bundles and buy a bare modem -- it's cheaper,
|
||
and lowers the likelihood that something vital to your communications
|
||
needs has been left out of the hardware.
|
||
|
||
Avoid "Class 1" and "Class 2" modems. Look for "Class 2.0" for the
|
||
full EIA-standard command set.
|
||
|
||
Fax capability is included with effectively all modems these days;
|
||
it's cheap for manufacturers, being basically a pure software add-on.
|
||
The CCITT also sets fax protocol standards. Terms to know:
|
||
|
||
V.29
|
||
CCITT standard for Group III fax encoding at 9600bps
|
||
|
||
V.17
|
||
CCITT standard for Group III fax encoding at 14400bps
|
||
|
||
There's a separate series of standards for software control of fax
|
||
modems over the serial (or USB) line maintained by the Electronics
|
||
Industry Association and friends. These are:
|
||
|
||
Class 1 -- base EIA standard for fax control as extensions to the
|
||
Hayes AT command set.
|
||
|
||
Class 2.0 -- enhanced EIA standard including compression, error
|
||
correction, station ID and other features.
|
||
|
||
Class 2 -- marketroidian for anything between Class 1 and Class 2.0.
|
||
Different "Class 2" modems implement different draft subsets of the
|
||
2.0 standard, so "Class 2" fax software won't necessarily drive any
|
||
given "Class 2" modem.
|
||
|
||
There's also a proprietary Intel "standard" called CAS, Communicating
|
||
Applications Specification. Ignore it; only Intel products support
|
||
it.
|
||
________________________________________________________________
|
||
|
||
3.11. Printers
|
||
|
||
The most important thing to optimize nowadays is cost of consumables.
|
||
Printer manufacturers, especially at the low end, have adopted a
|
||
model under which they sell printers with near-zero or even negative
|
||
margin, then gouge you horribly on the cost of cartridges and ink.
|
||
Common tactics include (a) shipping half-filled "starter" cartridges
|
||
with your printer, so you have to replace much sooner than you'd
|
||
think, (b) toner-empty sensors deliberately miscalibrated to blink
|
||
the error light on your printer when they're still a quarter to a
|
||
third full, and (c) electronic countermeasures to lock out cheap
|
||
third-party refills - in one notorious case, a printer manufacturer
|
||
used the DMCA to sue refill vebdoers who circumvented these!
|
||
|
||
Better dealers (the Staples chain, for example) will show you a chart
|
||
covering price and consumable-cost-per-page for all the models they
|
||
carry. If you don't see this, leave. When you do, estimate your
|
||
monthly print volume and trade off up-front against consumables
|
||
price. appropriately. Hint: The vendors count on you underestimating
|
||
your volume and consumables cost, and you usually will. Payiing a few
|
||
extra bucks up front to lower that cost is smart.
|
||
|
||
Other than that, there really isn't all that much to be said about
|
||
printers; the market is thoroughly commoditized and printer
|
||
capabilities pretty much independent of the rest of your hardware.
|
||
The PC-clone magazines will tell you what you need to know about
|
||
print quality, speed, features, etc. The business users they feed on
|
||
are obsessed with all these things.
|
||
|
||
(There used to be a problem with "GDI printers" and "WinPrinters"
|
||
that only worked with Windows --they required special drivers that
|
||
took over your CPU to do image processing, These were such a bad idea
|
||
that they have basically disappeared off the market.)
|
||
|
||
Most popular printers are supported by GhostScript, and so it's easy
|
||
to make them do PostScript. If you're buying any letter-quality
|
||
printer (laser or ink-jet), check to see if it's on GhostScript's
|
||
supported device list -- otherwise you'll have to pay a premium for
|
||
Postscript capability! Postscript is still high-end in the Windows
|
||
market, but it's ubiquitous in the Unix world.
|
||
|
||
Warning, however: if you're using ghostscript on a non-Postscript
|
||
printer, printspeed will be slow, especially with a serial printer. A
|
||
bitmapped 600 dpi page has a lot of pixels on it. At today's prices,
|
||
paying the small premium for Postscript capability makes sense.
|
||
|
||
If you're buying a printer for home, an inkjet is a good choice
|
||
because it doesn't use gobs of power and you won't have the
|
||
toner/ozone/noise/etc mess that you do with a laser. If all you want
|
||
is plain-ASCII, dot-matrix is cheaper to buy and run -- if you can
|
||
find one. Inexpensive ink-jets and lasers have almost driven them off
|
||
the market.
|
||
|
||
Inkjets are great in that they're cheap, many of them do color, and
|
||
there are many kinds which aren't PCL but are understood by
|
||
Ghostscript anyway. If you print very infrequently (less than weekly,
|
||
say), you should be careful to buy a printer whose print head gets
|
||
replaced with every ink cartrige: infrequent use can lead to the
|
||
drying of the ink, both in the ink cartrige and in the print head.
|
||
The print heads you don't replace with the cartrige tend to cost
|
||
nearly as much as the printer (~$200 for an Epson Stylus 800) once
|
||
the warranty runs out (the third such repair, just after the warranty
|
||
expired, totalled one informant's Stylus 800). Be careful, check
|
||
print head replacement costs ahead of time, and run at least a
|
||
cleaning cycle if you don't actually print anything in a given week.
|
||
(Conversely, toner starts out dry, and ribbon ink won't evaporate for
|
||
years...if you truly print only rarely, but neither a dot matrix nor
|
||
a laser makes sense, consider buying no printer and taking your
|
||
PostScript files to a copy shop...)
|
||
|
||
Nowadays, a lot of printers are moving away from parallel-port
|
||
interfaces to USB. This is a good idea, because USB devices announce
|
||
themselves to the host computer and can be automatically configured.
|
||
Parallel ports (and serial ports for that matter) are becoming
|
||
obsolete. Many new PC motherboards no longer include them.
|
||
|
||
Many printers (even some sub-$100 models) now come with a network
|
||
(10/100 Ethernet) interface. This make sharing them trivial, and also
|
||
avoids having to leave a desktop PC powered on so others (using
|
||
notebooks perhaps) can print to your printer. Therefore, such
|
||
printers are worth considering in many networked environments,
|
||
including home networks.
|
||
|
||
In the near future, new motherboards may stop including parallel and
|
||
serial ports altogether. That's another good reason to go with a USB-
|
||
or Ethernet-capable printer.
|
||
________________________________________________________________
|
||
|
||
3.12. Power Protection
|
||
|
||
I strongly recommend that you buy a UPS to protect your hardware and
|
||
data. MOV-filtered power bars make nice fuses (they're cheap to
|
||
replace), but they're not enough. I have written a UPS HOWTO that
|
||
provides more complete coverage of what used to be in this section.
|
||
________________________________________________________________
|
||
|
||
3.13. Radio Frequency Interference
|
||
|
||
(Thanks to Robert Corbett <Robert.Corbett@Eng.Sun.COM> for
|
||
contributing much of this section)
|
||
|
||
Radio Frequency Interference (RFI) is a growing problem with PC-class
|
||
machines. Today's processor speeds are such that the electromagnetic
|
||
noise generated by a PC's circuitry in normal operation can degrade
|
||
or jam radio and TV reception in the neighborhood. Such noise is
|
||
called Radio Frequency Interference (RFI). Computers, as transmitting
|
||
devices, are regulated by the Federal Communications Commission
|
||
(FCC).
|
||
|
||
FCC regulations recognize two classes of computer:
|
||
|
||
If a PC is to be used in a home or apartment, it must be certified to
|
||
be FCC class B. If it is not, neighbors have a legal right to prevent
|
||
its use. FCC class A equipment is allowed in industrial environments.
|
||
|
||
Many systems are not FCC class B. Some manufacturers build boxes that
|
||
are class B and then ship them with class A monitors or external disk
|
||
drives. Even the cables can be a source of RFI.
|
||
|
||
It pays to be cautious. For example, the Mag MX17F is FCC class B.
|
||
There are less expensive versions of the MX17 that are not. The Mag
|
||
MX17 is a great monitor. It would be painful to own one and not be
|
||
allowed to use it.
|
||
|
||
An upgradeable system poses special problems. A system that is FCC
|
||
class B with a 33 MHz CPU might not be when the CPU is upgraded to a
|
||
50 or 66 MHz CPU. Some upgrades require knockouts in the case to be
|
||
removed. If a knockout is larger than whatever replaces it, RFI can
|
||
leak out through the gap. Grounded metal shims can eliminate the
|
||
leaks.
|
||
|
||
Even Class B systems don't mix well with wireless phonesets (not
|
||
cellular phones, but the kind with a base station and antennaed
|
||
headset). You'll often find a wireless phone hard to use withing 20
|
||
feet of a Class B machine.
|
||
|
||
To cut down on RFI, get a good metal case with tight joints, or at
|
||
least make sure any plastic one you buy has a conductive lining. You
|
||
can also strip the painted metal-to-metal contacting parts of paint
|
||
so that there's good conductive metal contact. Paint's a poor
|
||
conductor in most cases, so you can get some benefit from this.
|
||
________________________________________________________________
|
||
|
||
4. What To Optimize
|
||
|
||
4.1. First, add more memory
|
||
|
||
Max out your memory. Having lots of free memory will improve your
|
||
virtual-memory performance (and Unix takes advantage of extra memory
|
||
more effectively than Windows does). Fortunately, with RAM as cheap
|
||
as it is now, a gigabyte or three is unlikely to bust your budget
|
||
even if you're economizing.
|
||
________________________________________________________________
|
||
|
||
4.2. Bus and Disk speeds
|
||
|
||
Most people think of the processor as the most important choice in
|
||
specifying any kind of personal-computer system. But for typical job
|
||
loads under Linux, the processor type is nearly a red herring -- it's
|
||
far more important to specify a capable system bus and disk I/O
|
||
subsystem. If you don't believe this, you may find it enlightening to
|
||
keep top(1) running for a while as you use your machine. Notice how
|
||
seldom the CPU idle percentage drops below 90%!
|
||
|
||
It's true that after people upgrade their motherboards they often do
|
||
report a throughput increase. But this is often more due to other
|
||
changes that go with the processor upgrade, such as improved cache
|
||
memory or an increase in the clocking speed of the system's
|
||
front-side bus (enabling data to get in and out of the processor
|
||
faster).
|
||
|
||
If you're buying for Linux on a fixed budget, it makes sense to trade
|
||
away some excess processor clocks to get a faster bus and disk
|
||
subsystem. If you're building a monster hot-rod, go ahead and buy
|
||
that fastest available processor -- but once you've gotten past that
|
||
gearhead desire for big numbers, pay careful attention to bus speeds
|
||
and your disk subsystem, because that's where you'll get the serious
|
||
performance wins. The gap between processor speed and I/O subsystem
|
||
throughput has only widened in the last five years.
|
||
|
||
How does it translate into a recipe in 2010? Like this; if you're
|
||
building a hot rod,
|
||
|
||
* Do buy a machine with the fastest available "front-side" (e.g.
|
||
processor-to-memory) bus.
|
||
* Do get the fastest SATA disks you can get your hands on.
|
||
________________________________________________________________
|
||
|
||
4.3. Optimizing your disk subsystem
|
||
|
||
For the fastest disks you can find, pay close attention to average
|
||
seek and latency time. The former is an average time required to seek
|
||
to any track; the latter is the maximum time required for any sector
|
||
on a track to come under the heads, and is a function of the disk's
|
||
rotation speed.
|
||
|
||
Of these, average seek time is much more important. When you're
|
||
running Linux or any other virtual-memory operating system, a one
|
||
millisecond faster seek time can make a really substantial difference
|
||
in system throughput. Back when PC processors were slow enough for
|
||
the comparison to be possible (and I was running System V Unix), it
|
||
was easily worth as much as a 30MHz increment in processor speed.
|
||
Today the corresponding figure would probably be as much as 300MHz!
|
||
|
||
The manufacturers themselves avoid running up seek time on the
|
||
larger-capacity drives by stacking platters vertically rather than
|
||
increasing the platter size. Thus, seek time (which is proportional
|
||
to the platter radius and head-motion speed) tends to be constant
|
||
across different capacities in the same product line. This is good
|
||
because it means you don't have to worry about a capacity-vs.-speed
|
||
tradeoff.
|
||
|
||
Average drive latency is inversely proportional to the disk's
|
||
rotational speed. For years, most disks spun at 3600 rpm; most disks
|
||
now spin at 7,200 or 10,000rpm, and high-end disks at 15,000 rpm.
|
||
These fast-spin disks run extremely hot; cooling is becoming a
|
||
critical constraint in drive design.
|
||
|
||
For years, your basic decision was SATA vs. SCSI (the older IDE and
|
||
EIDE buses are long obsolete). Not in 2009; SATA 3 devices and
|
||
controllers are good enough that the performance advantage of SCSI is
|
||
marginal unless you are designing a super-high-end server box -
|
||
slightly faster transfer speeds (320MB/s vs. 300MB/s) and slightly
|
||
better susrained throughput.
|
||
|
||
The SCSI price premium entailed in an extra controller and more
|
||
expensive disks are no longer worth it for the home builder, even
|
||
from the point of view of grizzled old SCSI partisans like me.
|
||
Accordingly, I've dropped most of the detailed SCSI information I
|
||
used to carry here.
|
||
|
||
Final note: Solid-state drives loom on the horizon as replacements
|
||
for SATA disks, but the price per megabyte is still high enough that
|
||
as yet they're only being deployed in small capacities on netbooks.
|
||
Watch this space.
|
||
________________________________________________________________
|
||
|
||
4.4. Tuning Your I/O Subsystem
|
||
|
||
(This section comes to us courtesy of Perry The Cynic,
|
||
<perry@sutr.cynic.org>; it was written in 1998. My own experience
|
||
agrees pretty completely with his. I have revised the numbers in it
|
||
since to reflect more recent developments.)
|
||
|
||
Building a good I/O subsystem boils down to two major points: pick
|
||
matched components so you don't over-build any piece without benefit,
|
||
and construct the whole pipe such that it can feed what your
|
||
OS/application combo needs.
|
||
|
||
It's important to recognize that "balance" is with respect to not
|
||
only a particular processor/memory subsystem, but also to a
|
||
particular OS and application mix. A Unix server machine running the
|
||
whole TCP/IP server suite has radically different I/O requirements
|
||
than a video-editing workstation. For the "big boys" a good
|
||
consultant will sample the I/O mix (by reading existing system
|
||
performance logs or taking new measurements) and figure out how big
|
||
the I/O system needs to be to satisfy that app mix. This is not
|
||
something your typical Linux buyer will want to do; for one, the
|
||
application mix is not static and will change over time. So what
|
||
you'll do instead is design an I/O subsystem that is internally
|
||
matched and provides maximum potential I/O performance for the money
|
||
you're willing to spend. Then you look at the price points and
|
||
compare them with those for the memory subsystem. That's the most
|
||
important trade-off inside the box.
|
||
|
||
So the job now is to design and buy an I/O subsystem that is well
|
||
matched to provide the best bang for your buck. The two major
|
||
performance numbers for disk I/O are latency and bandwidth. Latency
|
||
is how long a program has to wait to get a little piece of random
|
||
data it asked for. Bandwidth is how much contiguous data can be sent
|
||
to/from the disk once you've done the first piece. Latency is
|
||
measured in milliseconds (ms); bandwidth in megabytes per second
|
||
(MB/s). Obviously, a third number of interest is how big all of your
|
||
disks are together (how much storage you've got), in Gigabytes (GB).
|
||
|
||
Within a rather big envelope, minimizing latency is the cat's meow.
|
||
Every millisecond you shave off effective latency will make your
|
||
system feel significantly faster. Bandwidth, on the other hand, only
|
||
helps you if you suck a big chunk of contiguous data off the disk,
|
||
which happens rarely to most programs. You have to keep bandwidth in
|
||
mind to avoid mis-matching pieces, because (obviously) the lowest
|
||
usable bandwidth in a pipe constrains everything else.
|
||
|
||
I'm going to ignore IDE. IDE is no good for multi-processing systems,
|
||
period. You may use an IDE CD-ROM if you don't care about its
|
||
performance, but if you care about your I/O performance, go SCSI.
|
||
(Beware that if you mix an IDE CD-ROM with SCSI drives under Linux,
|
||
you'll have to run a SCSI emulation layer that is a bit flaky.)
|
||
|
||
Let's look at the disks first. Whenever you seriously look at a disk,
|
||
get its data sheet. Every reputable manufacturer has them on their
|
||
website; just read off the product code and follow the bouncing
|
||
lights. Beware of numbers (`<12ms fast!') you may see in ads; these
|
||
folks often look for the lowest/highest numbers on the data sheet and
|
||
stick them into the ad copy. Not dishonest (usually), but ignorant.
|
||
|
||
What you need to find out for a disk is:
|
||
|
||
1. What kind of SCSI interface does it have? Look for "fast",
|
||
"ultra", and "wide". Ignore disks that say "fiber" (this is a
|
||
specialty physical layer not appropriate for the insides of small
|
||
computers). Note that you'll often find the same disk with
|
||
different interfaces.
|
||
2. What is the "typical seek" time (ms)? Make sure you get
|
||
"typical", not "track-to-track" or "maximum" or some other
|
||
measure (these don't relate in obvious ways, due to things like
|
||
head-settling time).
|
||
3. What is the rotational speed? This is typically 4500, 5400, 7200,
|
||
10000, or 15000 rpm (rotations per minute). Also look for
|
||
"rotational latency" (in ms). (In a pinch, average rotational
|
||
latency is approx. 30000/rpm in milliseconds.)
|
||
4. What is the `media transfer rate' or speed (in MB/s)? Many disks
|
||
will have a range of numbers (say, 7.2-10.8MB/s). Don't confuse
|
||
this with the "interface transfer rate" which is always a round
|
||
number (10 or 20 or 40MB/s) and is the speed of the SCSI bus
|
||
itself.
|
||
|
||
These numbers will let you do apple-with-apples comparisons of disks.
|
||
Beware that they will differ on different-size models of the same
|
||
disk; typically, bigger disks have slower seek times.
|
||
|
||
Now what does it all mean? Bandwidth first: the `media transfer rate'
|
||
is how much data you can, under ideal conditions, get off the disk
|
||
per second. This is a function mostly of rotation speed; the faster
|
||
the disk rotates, the more data passes under the heads per time unit.
|
||
This constrains the sustained bandwidth of this disk.
|
||
|
||
More interestingly, your effective latency is the sum of typical seek
|
||
time and rotational latency. So for a disk with 8.5ms seek time and
|
||
4ms rotational latency, you can expect to spend about 12.5ms between
|
||
the moment the disk `wants' to read your data and the moment when it
|
||
actually starts reading it. This is the one number you are trying to
|
||
make small. Thus, you're looking for a disk with low seek times and
|
||
high rotation (RPM) rates.
|
||
|
||
For comparison purposes, the first hard drive I ever bought was a
|
||
20MB drive with 65ms seek time and about 3000RPM rotation. A floppy
|
||
drive has about 100-200ms seek time. A CD-ROM drive can be anywhere
|
||
between 120ms (fast) and 400ms (slow). The best IDE harddrives have
|
||
about 10-12ms and 5400 rpm. The best SCSI harddrive I know (the
|
||
Fujitsu MAM) runs 3.9ms/15000rpm.
|
||
|
||
Fast, big drives are expensive. Really big drives are very expensive.
|
||
Really fast drives are pretty expensive. On the other end, really
|
||
slow, small drives are cheap but not cost effective, because it
|
||
doesn't cost any less to make the cases, ship the drives, and sell
|
||
them.
|
||
|
||
In between is a `sweet spot' where moving in either direction
|
||
(cheaper or more expensive) will cost you more than you get out of
|
||
it. The sweet spot moves (towards better value) with time. If you can
|
||
make the effort, go to your local computer superstore and write down
|
||
a dozen or so drives they sell `naked'. (If they don't sell at least
|
||
a dozen hard drives naked, find yourself a better store. Use the Web,
|
||
Luke!) Plot cost against size, seek and rotational speed, and it will
|
||
usually become pretty obvious which ones to get for your budget.
|
||
|
||
Do look for specials in stores; many superstores buy overstock from
|
||
manufacturers. If this is near the sweet spot, it's often
|
||
surprisingly cheaper than comparable drives. Just make sure you
|
||
understand the warranty procedures.
|
||
|
||
Note that if you need a lot of capacity, you may be better off with
|
||
two (or more) drives than a single, bigger one. Not only can it be
|
||
cheaper but you end up with two separate head assemblies that move
|
||
independently, which can cut down on latency quite a bit (see below).
|
||
|
||
If you find yourself at the high end of the bandwidth game, be aware
|
||
that the theoretical maximum of the PCI bus itself is 132MB/s. That
|
||
means that a dual ultra/wide SCSI controller (2x40MB/s) can fill more
|
||
than half of the PCI bus's bandwidth, and it is not advised to add
|
||
another fast controller to that mix. As it is, your device driver
|
||
better be well written, or your entire system will melt down
|
||
(figuratively speaking).
|
||
|
||
Incidentally, all of the numbers I used are `optimal' bandwidth
|
||
numbers. The real scoop is usually somewhere between 50-70% of
|
||
nominal, but things tend to cancel out -- the drives don't quite
|
||
transfer as fast as they might, but the SCSI bus has overhead too, as
|
||
does the controller card.
|
||
|
||
Whether you have a single disk or multiple ones, on one or several
|
||
SCSI buses, you should give careful thought to their partition
|
||
layout. Given a set of disks and controllers, this is the most
|
||
crucial performance decision you'll make.
|
||
|
||
A partition is a contiguous group of sectors on the disk.
|
||
Partitioning typically starts at the outside and proceeds inwards.
|
||
All partitions on one disk share a single head assembly. That means
|
||
that if you try to overlap I/O on the first and last partition of a
|
||
disk, the heads must move full stroke back and forth over the disk,
|
||
which can radically increase seek time delays. A partition that is in
|
||
the middle of a partition stack is likely to have best seek
|
||
performance, since at worst the heads only have to move half-way to
|
||
get there (and they're likely to be around the area anyway).
|
||
|
||
Whenever possible, split partitions that compete onto different
|
||
disks. For example, /usr and the swap should be on different disks if
|
||
at all possible (unless you have outrageous amounts of RAM).
|
||
|
||
Another wrinkle is that most modern disks use `zone sectoring'. The
|
||
upshot is that outside partitions will have higher bandwidth than
|
||
inner ones (there is more data under the heads per revolution). So if
|
||
you need a work area for data streaming (say, a CD-R pre-image to
|
||
record), it should go on an outside (early numbered) partition of a
|
||
fast-rotating disk. Conversely, it's a good convention to put
|
||
rarely-used, performance-uncritical partitions on the inside (last).
|
||
|
||
Ah yes, caches. There are three major points where you could cache
|
||
I/O buffers: the OS, the controller card or chip in your machine, and
|
||
the on-disk controller. Intelligent OS caching is by far the biggest
|
||
win, for many reasons. RAM caches on controller cards are pretty
|
||
pointless these days; you shouldn't pay extra for them, and
|
||
experiment with disabling them if you're into tinkering.
|
||
|
||
RAM caches on the drives themselves are a mixed bag. At moderate size
|
||
(1-2MB), they are a potential big win for Windows 95/98, because
|
||
Windows has stupid VM and I/O drivers. If you run a true
|
||
multi-tasking OS like Linux, having unified RAM caches on the disk is
|
||
a significant loss, since the overlapping I/O threads kick each other
|
||
out of the cache, and the disk ends up performing work for nothing.
|
||
|
||
Most high-performance disks can be reconfigured (using mode page
|
||
parameters, see above) to have `segmented' caches (sort of like a
|
||
set-associative memory cache). With that configured properly, the RAM
|
||
caches can be a moderate win, not because caching is so great on the
|
||
disk (it's much better in the OS), but because it allows the disk
|
||
controller more flexibility to reschedule its I/O request queue. You
|
||
won't really notice it unless you routinely have >2 I/O requests
|
||
pending at the SCSI level. The conventional wisdom (try it both ways)
|
||
applies.
|
||
|
||
And finally I do have to make a disclaimer. Much of the stuff above
|
||
is shameless simplification. In reality, high-performance disks are
|
||
very complicated beasties. They run little mini-operating systems
|
||
that are most comfortable if they have 10-20 I/O requests pending at
|
||
the same time. Under those circumstances, the amortized global
|
||
latencies are much reduced, though any single request may experience
|
||
longer latencies than if it were the only one pending. The only
|
||
really valid analysis are stochastic-process models, which we really
|
||
don't want to get into here. :-)
|
||
________________________________________________________________
|
||
|
||
5. But What If I'm Economizing?
|
||
|
||
If you are economizing, here's a simple rule:
|
||
|
||
* Do buy a CPU/motherboard one or two levels lower than commercial
|
||
state of the art.
|
||
|
||
For best value, look in the middle of the current range of available
|
||
processors. On the desktop, in late 2007, that means a CPU costing
|
||
perhaps $75 to $200, not the latest and greatest quad core marvels
|
||
selling for several times that!
|
||
|
||
Why? Because of the way manufacturers' price-performance curves are
|
||
shaped. The top-of-line system is generally boob bait for corporate
|
||
executives and other people with more money than sense. Chances are
|
||
the system design is new and untried -- if you're at the wrong point
|
||
in the technology cycle, the chip may even be a pre-production
|
||
sample, or an early production stepping with undiscovered bugs like
|
||
the infamous FDIV problem in early Pentiums. You don't need such
|
||
troubles. Better to go with a chip/motherboard combination that's
|
||
been out for a while and is known good. It's not like you really need
|
||
the extra speed, after all.
|
||
|
||
Besides, if you buy one of these gold-plated systems, you're only
|
||
going to kick yourself three months later when the price plunges by
|
||
30%. Further down the product line there's been more real competition
|
||
and the manufacturer's margins are already squeezed. There's less
|
||
room for prices to fall, so you won't watch your new toy lose street
|
||
value so fast. Its price will still drop, but it won't plummet
|
||
sickeningly.
|
||
|
||
Again, bear in mind that the cheapest processor you can buy new today
|
||
is plenty fast enough for Linux. So if dropping back a speed level or
|
||
two brings you in under budget, you can do it with no regrets.
|
||
|
||
Consider one drive rather than two. This will reduce overall system
|
||
performance somewhat, but the cost saving as a fraction of total
|
||
system cost is often substantial.
|
||
|
||
Another easy economy measure is looking for repaired or reconditioned
|
||
parts with a warranty. These are often as good as new, and much
|
||
cheaper.
|
||
|
||
Your display is one of the areas where pinching pennies is not a good
|
||
idea. You're going to be looking at that display for hours on end.
|
||
You are going to be using the screen real estate constantly. Buy the
|
||
best quality, largest screen you possibly can -- it will be worth it.
|
||
|
||
Similarly, do not reduce the amount of RAM in your system too far. A
|
||
minimum of 4GB of RAM is helpful in desktop systems today.
|
||
________________________________________________________________
|
||
|
||
6. Noise Control and Heat Dissipation
|
||
|
||
An increasingly critical aspect of machine design is handling the
|
||
waste heat and acoustic noise of operation. This may seem like a
|
||
boring subject, but cooling is a centrally important one if you want
|
||
your machine to last -- because thermal stress from the electronics'
|
||
own waste heat is almost certainly what will kill it. You want that
|
||
fatal moment to happen later rather than sooner. On the other hand,
|
||
cooling makes acoustic noise, which human beings don't tolerate well.
|
||
|
||
This tradeoff bites harder than you think; it's the fundamental
|
||
reason that, despite my money-is-no-object premise in the Ultimate
|
||
Linux Box artcles, I didn't go to relatively exotic technologies like
|
||
liquid-cooled overclocking or RAID disk arrays for a performance
|
||
boost. Sure, they may initially look attractive -- but overclocked
|
||
chips and banks of disk drives require massive cooling with lots of
|
||
moving parts, and it's not good to be trying to do creative work like
|
||
programming with anything that sounds quite so much like an idling
|
||
jet engine sitting beside one's desk.
|
||
|
||
In 2001 we had already reached the point at which the thermal load
|
||
vs. cooling-noise tradeoff is the effective limiting factor in the
|
||
performance of personal machines. Ten years ago, even low-end and
|
||
medium "server" machines differed from personal-PC designs in fairly
|
||
important ways (different processor and bus types, different speed
|
||
ranges, etc.) Nowadays specialized server architectures are in
|
||
retreat at the high end of the market and everything else looks like
|
||
a PC. And the difference between a "PC" and a "server" is mainly that
|
||
servers live in server rooms, and are allowed to have monster cases
|
||
with lots of noisy fans.
|
||
|
||
So how do we manage this tradeoff for a personal, desktop or
|
||
desk-side machine? Careful choice of components and being willing to
|
||
pay some price premium for cool-running and low-noise characteristics
|
||
can help a lot. Even exceptionally clueful system integrators can't
|
||
generally afford to do this, because they're under constant
|
||
competitive pressure to cut price and costs by using generic
|
||
components.
|
||
|
||
Reducing expected noise and heat in a design call for different
|
||
strategies. It's relatively easy to find decibel figures for the
|
||
noisemaking parts in a PC design. And, once you know a little basic
|
||
audiometry and a few basic rules of thumb, it's not hard to form a
|
||
fair estimate of your design's noisiness. Estimating a design's heat
|
||
dissipation is harder, partly because the waste-heat emission of a
|
||
PC's subsystems tends to vary in a more complex way than the acoustic
|
||
emissions of the mechanical parts. This means that you can and should
|
||
try to design ahead for low noise, but on the other hand expect to
|
||
have to monitor for heat-dissipation problems in your prototype and
|
||
solve them by building in more cooling.
|
||
|
||
Here's the basic audiometry you need to know to control your design's
|
||
noise emissions:
|
||
|
||
Sound is measured in decibels, abbreviated dB, relative to the
|
||
threshold of audibility, "A". (Thus, sound levels above that
|
||
threshold are written "dBA".) The scale is logarithmic, with every
|
||
3dB increment roughly doubling sound intensity.
|
||
|
||
For sounds that are not phase-related, decibel levels add as a
|
||
logarithmic sum. Thus if X and Y are uncorrelated sound sources,
|
||
|
||
dBA(X + Y) = 10 * log(10 ^ (dBA(X)/10) + 10 ^ (dBA(Y)/10))
|
||
|
||
A consequence of the above formula is that dBA(X + Y) cannot be more
|
||
than 3dB above the greater of dBA(X) and dBA(Y) for uncorrelated
|
||
sources (6dB for perfectly correlated ones).
|
||
|
||
Sound from a point source decays by an inverse-square law, roughly
|
||
6dB for each doubling of distance.
|
||
|
||
Important thresholds on the decibel scale:
|
||
|
||
0 dBA
|
||
Threshold of hearing
|
||
|
||
20 dBA
|
||
Rustling leaves, quiet living room
|
||
|
||
30 dBA
|
||
Quiet office
|
||
|
||
40 dBA
|
||
Quiet conversation
|
||
|
||
45 dBA
|
||
Threshold of distraction, according to EPA
|
||
|
||
50 dBA
|
||
Quiet street, average office noise
|
||
|
||
60 dBA
|
||
Normal conversation (1 foot distance)
|
||
|
||
70 dBA
|
||
Inside car
|
||
|
||
75 dBA
|
||
Loud singing (3 feet)
|
||
|
||
80 dBA
|
||
Typical home-stereo listening level
|
||
|
||
The acoustic noise emitted by PCs is normally a combination of white
|
||
noise produced by airflow, high-frequency noise produced by bearing
|
||
friction in drive spindles and fans, and the constant frequency
|
||
"blade passing" noise that all propellers emit (the latter is often
|
||
more intense than white noise and bearing whine).
|
||
|
||
The best low-noise ball-bearing case fans emit around 20dBA. Typical
|
||
sleeve-bearing fans emit 30-50dBA.
|
||
|
||
According to the indispensable [http://tomshardware.com/] Tom's
|
||
Hardware site, you can expect to cut at least 5dB off the interior
|
||
noise level of the computer with a good choice of case. We'll improve
|
||
on that by adding sound-absorbing material to the interior.
|
||
________________________________________________________________
|
||
|
||
7. Special Considerations When Buying Laptops and Netbboks
|
||
|
||
First, don't be misled by the term "netbook". A netbook is just a
|
||
small, low-priced, low-power laptop with relatively small solid-state
|
||
drives. Because the display and drive capacity are small, netbooks
|
||
are basically just good for email and surfing. If you're going to do
|
||
coding or even much word processing you'll need something more like a
|
||
traditional laptop or desktop.
|
||
|
||
Up until about 1999 the laptop market was completely crazy. The
|
||
technology was in a state of violent flux, with "standards" phasing
|
||
in and out and prices dropping like rocks. Things are beginning to
|
||
settle out a bit more now.
|
||
|
||
One sign of this change is that there are now a couple of laptop
|
||
lines that are clear best-of-breeds for reasons having as much to do
|
||
with good industrial design and ergonomics as the technical details
|
||
of the processor and display.
|
||
|
||
In lightweight machines, I was a big fan of the Sony VAIO line. I
|
||
owned one from early 1999 until it physically disintegrated under the
|
||
rigors of travel in late 2000, and could hardly imagine switching.
|
||
They weigh 3.5 pounds, give you an honest 3 hours of life per
|
||
detachable battery pack, have a very nice 1024x768 display, and are
|
||
just plain pretty. Their only serious drawback is that they're not
|
||
rugged, and often fall apart after a year or so of use.
|
||
|
||
If you want a full-power laptop that can compete with or replace your
|
||
desktop machine, the Lenovo (formerly IBM) ThinkPad line is the bomb.
|
||
Capable, rugged, and nicely designed. I now use a ThinkPad X61, the
|
||
lightest and smallest machine in the line, and like it a lot.
|
||
|
||
These machines are not cheap, though. If you're trying to save money
|
||
by buying a no-name laptop, here are things to look for:
|
||
|
||
First: despite what you may believe, the most important aspect of any
|
||
laptop is not the CPU, or the disk, or the memory, or the screen, or
|
||
the battery capacity. It's the keyboard feel, since unlike in a PC,
|
||
you cannot throw the keyboard away and replace it with another one
|
||
unless you replace the whole computer. Never buy any laptop that you
|
||
have not typed on for a couple hours. Trying a keyboard for a few
|
||
minutes is not enough. Keyboards have very subtle properties that can
|
||
still affect whether they mess up your wrists.
|
||
|
||
A standard desktop keyboard has keycaps 19mm across with 7.55mm
|
||
between them. If you plot frequency of typing errors against keycap
|
||
size, it turns out there's a sharp knee in the curve at 17.8
|
||
millimeters. Beware of "kneetop" and "palmtop" machines, which
|
||
squeeze the keycaps a lot tighter and typically don't have enough
|
||
oomph for Unix anyway; you're best off with the "notebook" class
|
||
machines that have full-sized keys.
|
||
|
||
Second: with present flatscreens, 1920x1200 color is the best you're
|
||
going to do (and that is on a 17in widescreen, which translates to a
|
||
large notebook. On normal size notebooks, a maximum of 1440x900 is
|
||
more common). On travel machines like the Lenovo X serties, you're
|
||
still stuck with 1024x768. If you want more than that (for X, for
|
||
example) you have to either fall back to a desktop or make sure
|
||
there's an external-monitor port on the laptop (and many laptops
|
||
won't support higher resolution than the flatscreen's).
|
||
|
||
Third: about those vendor-supplied time-between-recharge figures;
|
||
don't believe them. They collect those from a totally quiescent
|
||
machine, sometimes with the screen or hard disk turned off. Under
|
||
Windows, you'd be lucky to get half the endurance they quote; under
|
||
Unix, which hits the disk more often, it may be less yet. Figures
|
||
from magazine reviews are more reliable.
|
||
|
||
Fourth: You can now avoid many of the driver hassles involved in
|
||
getting some devices on your notebook to work (or week well) under
|
||
Linux by purchasing a notebook with Linux pre-installed. Dell has
|
||
recently started to make noise in this regard in the Linux community.
|
||
Taking this approach limits the set of notebooks you can consider,
|
||
but the one you get is likely to "just work" (including sound, useful
|
||
capabilities like suspend/resume, and even hotplugging of external
|
||
displays and projectors) to a much higher degree under Linux than
|
||
others.
|
||
________________________________________________________________
|
||
|
||
8. How to Buy
|
||
|
||
8.1. When to Buy
|
||
|
||
It used to be that good configurations for Unix were what the market
|
||
called `server' machines, with beefed-up I/O subsystems and fast
|
||
buses. No longer; today's `servers' are monster boxes with multiple
|
||
power supplies and processors, gigabytes of memory, and
|
||
industrial-grade air cooling --they're not really suitable as
|
||
personal machines. A typical SCSI desktop workstation is as much as
|
||
you'll need.
|
||
|
||
Prices keep dropping, so there's a temptation to wait forever to buy.
|
||
A good way to cope with this is to configure your system on paper,
|
||
get a couple of initial estimates, then set a trigger price, below
|
||
the lowest one, at what you're willing to pay. Then watch and wait.
|
||
When the configuration cost hits your trigger price, place your
|
||
order.
|
||
|
||
The advantage of this method is that it requires you to settle in
|
||
your mind, well in advance, what you're willing to pay for what
|
||
you're getting. That way, you'll buy at the earliest time you should,
|
||
and won't stress too much out afterwards as it depreciates.
|
||
|
||
Before you shop, do your homework. Publications like "Computer
|
||
Shopper" (and their web site at [http://www.computershopper.com]
|
||
http://www.computershopper.com) are invaluable for helping you get a
|
||
feel for prices and what clonemakers are doing. Another excellent
|
||
site is [http://www.computeresp.com] ComputerESP.
|
||
________________________________________________________________
|
||
|
||
8.2. Where to Buy
|
||
|
||
The most important where-to-buy advice is negative. Do not go to a
|
||
traditional, business-oriented storefront dealership. Their overheads
|
||
are high. So are their prices.
|
||
|
||
Especially, run --do not walk --away from any outfit that trumpets
|
||
`business solutions'. This is marketing code for the kind of place
|
||
that will justify a heavy price premium by promising after-sale
|
||
service and training which, nine times out of ten, will turn out to
|
||
be nonexistent or incompetent. Sure, they'll give you plush carpeting
|
||
and a firm handshake from a guy with too many teeth and an expensive
|
||
watch --but did you really want to pay for that?
|
||
|
||
There are two major alternatives to storefront dealerships and one
|
||
minor one. The major ones are mail order and computer superstores.
|
||
The minor one is computer fairs.
|
||
________________________________________________________________
|
||
|
||
8.3. Computer Fairs
|
||
|
||
I used to be a big fan of hole-in-the-wall stores run by immigrants
|
||
from the other side of the International Date Line, but most of those
|
||
places have been driven out of the regular retail game by the
|
||
superstores and the Web. If you still have one in your neighborhood,
|
||
you're lucky. I do, as it happens, but that is now unusual; the only
|
||
place you normally find diaspora Chinese and Indians selling cheap
|
||
PCs over the counter anymore is at computer fairs. (Usually they're
|
||
doing it to publicize an Internet/mail-order business.)
|
||
|
||
You can find good loss-leader deals on individual parts at these
|
||
fairs (they're especially good places to buy disk drives cheap). But
|
||
I call them a minor alternative because it's hard to get a custom
|
||
configuration tuned for Unix built for you at a fair. So you end up,
|
||
effectively, back in the mail-order or Web channel.
|
||
________________________________________________________________
|
||
|
||
8.4. Mail Order
|
||
|
||
Internet buying makes a lot of sense today for anyone with more
|
||
technical savvy than J. Random Luser in a suit. Even from no-name
|
||
vendors, parts and system quality tend to be high and consistent, so
|
||
conventional dealerships don't really have much more to offer than a
|
||
warm fuzzy feeling. Furthermore, competition has become so intense
|
||
that even Internet/mail-order vendors today have to offer not just
|
||
lower prices than ever before but warranty and support policies of a
|
||
depth that would have seemed incredible a few years back. For
|
||
example, many bundle a year of on-site hardware support with their
|
||
medium- and high-end "business" configurations for a very low premium
|
||
over the bare hardware.
|
||
|
||
Note, however, that assembling a system yourself out of parts is not
|
||
likely to save you money over dealing with the Internet/mail-order
|
||
systems houses. You can't buy parts at the volume they do; the
|
||
discounts they command are bigger than the premiums reflected in
|
||
their prices. The lack of any system warranty or support can also be
|
||
a problem even if you're expert enough to do the integration yourself
|
||
-- because you also assume all the risk of defective parts and
|
||
integration problems.
|
||
|
||
Watch out for dealers (Spectrum Trading for one) who charge
|
||
ridiculous shipping fees. One of our spies reports he bought a
|
||
hotswappable hard disc drive tray that weighed about 3 lbs. and cost
|
||
$250 and they charged $25 to ship it UPS groud.
|
||
|
||
Don't forget that (most places) you can avoid sales tax by buying
|
||
from an out-of-state outfit, and save yourself 6-8% depending on
|
||
where you live. If you live near a state line, buying from a local
|
||
outfit you can often win, quite legally, by having the stuff shipped
|
||
to a friend or relative just over it. Best of all is a buddy with a
|
||
state-registered dealer number; these aren't very hard to get and
|
||
confer not just exemption from sales tax but (often) whopping
|
||
discounts from the vendors. Hand him a dollar afterwards to make it
|
||
legal.
|
||
|
||
(Note: I have been advised that you shouldn't try the latter tactic
|
||
in Florida --they are notoriously tough on "resale license" holders).
|
||
|
||
(Note II: The Supreme Court has ruled that states may not tax
|
||
out-of-state businesses under existing law, but left the way open for
|
||
Congress to pass enabling legislation. Let's hope the mail-order
|
||
industry has good lobbyists.)
|
||
________________________________________________________________
|
||
|
||
8.5. Computer Superstores
|
||
|
||
Big chain superstores like CompUSA give you a reasonable alternative
|
||
to the Web. And there are good reasons to explore it -- these stores
|
||
buy and sell at volumes that allow them to offer prices not far above
|
||
the Web. (They make back a lot of their margin on computer games and
|
||
small accessories like mouse pads, cables, and floppy disks.)
|
||
|
||
Note, however: Avoid Best Buy. Horror stories about them are legion
|
||
-- predatory salescritters, incompetent service, routine
|
||
bait-and-switch tactics.
|
||
|
||
One thing you should not buy remotely if you can avoid it is a
|
||
monitor. Monitors are subject to significant quality variations even
|
||
within the same make and model. Flatscreens haver this [roblem less
|
||
than CRTs did, but you don't want a flatscreen with dead pixels. So
|
||
buy your monitor face-to-face, picking the best out of three or four.
|
||
|
||
Another good argument for buying at a superstore is that you may have
|
||
to pay return postage if you ship a system back to the vendor. On a
|
||
big, heavy system, this can eat your initial price savings.
|
||
|
||
The only major problem with superstores is that the salespeople who
|
||
staff them aren't very bright or very clueful (it's a sort of
|
||
Darwinian reverse-selection effect; these are the guys who are
|
||
fascinated by computer technology but not smart enough to be
|
||
techies). Most of them don't know from Linux and are likely to push
|
||
things like two-button mice that you can't use. Use caution and check
|
||
your system manifest.
|
||
|
||
But if you shop carefully and don't fall for one of their name-brand
|
||
"prestige" systems, you can get prices comparable to
|
||
Internet/mail-order with the comfort of knowing there's a trouble
|
||
desk you can drive back to in a pinch. (Also, you can see your
|
||
monitor before you buy!)
|
||
________________________________________________________________
|
||
|
||
8.6. Other Buying Tips
|
||
|
||
You can often get out of paying tax just by paying cash, especially
|
||
at computer shows. You can always say you're going to ship the
|
||
equipment out of the state.
|
||
|
||
A lot of vendors bundle Windows and variable amounts of apps with
|
||
their hardware. If you tell them to lose all this useless cruft they
|
||
may shave $50 or $100 off the system price.
|
||
________________________________________________________________
|
||
|
||
9. Questions You Should Always Ask Your Vendor
|
||
|
||
9.1. Minimum Warranty Provisions
|
||
|
||
The weakest guarantee you should settle for in the mail-order market
|
||
should include:
|
||
|
||
* 72-hour burn-in to avoid that sudden infant death syndrome.
|
||
(Also, try to find out if they do a power-cycling test and how
|
||
many repeats they do; this stresses the hardware much more than
|
||
steady burn-in.)
|
||
* 30 day money-back guarantee. Watch out for fine print that
|
||
weakens this with a restocking fee or limits it with exclusions.
|
||
* 1 year parts and labor guarantee (some vendors give 2 years).
|
||
* 1 year of 800 number tech support (many vendors give lifetime
|
||
support).
|
||
|
||
Additionally, many vendors offer a year of on-site service free. You
|
||
should find out who they contract the service to. Also be sure the
|
||
free service coverage area includes your site; some unscrupulous
|
||
vendors weasel their way out with "some locations pay extra", which
|
||
translates roughly to "through the nose if you're further away than
|
||
our parking lot".
|
||
|
||
If you're buying store-front, find out what they'll guarantee beyond
|
||
the above. If the answer is "nothing", go somewhere else.
|
||
________________________________________________________________
|
||
|
||
9.2. Documentation
|
||
|
||
Ask your potential suppliers what kind and volume of documentation
|
||
they supply with your hardware. You should get, at minimum,
|
||
operations manuals for the motherboard and each card or peripheral;
|
||
also an IRQ list. Skimpiness in this area is a valuable clue that
|
||
they may be using no-name parts from Upper Baluchistan, which is not
|
||
necessarily a red flag in itself but should prompt you to ask more
|
||
questions.
|
||
________________________________________________________________
|
||
|
||
9.3. A System Quality Checklist
|
||
|
||
There are various cost-cutting tactics a vendor can use which bring
|
||
down the system's overall quality. Here are some good questions to
|
||
ask:
|
||
|
||
* If you're buying a factory-configured system, does it have FCC
|
||
certification? While it's not necessarily the case that a
|
||
non-certified system is going to spew a lot of radio-frequency
|
||
interference, certification is legally required -- and becoming
|
||
more important as clock frequencies climb. Lack of that sticker
|
||
may indicate a fly-by-night vendor, or at least one in danger of
|
||
being raided and shut down! (For further discussion, see the
|
||
section on Radio Frequency Interference above.)
|
||
* Are the internal cable connectors keyed, so they can't be put in
|
||
upside down? This doesn't matter if you'll never, ever ever need
|
||
to upgrade or service your system. Otherwise, it's pretty
|
||
important; and, vendors who fluff this detail may be quietly
|
||
cutting other corners.
|
||
________________________________________________________________
|
||
|
||
10. Things to Check when Buying
|
||
|
||
10.1. Tricks and Traps in Warranties
|
||
|
||
Reading warranties is an art in itself. A few tips:
|
||
|
||
Beware the deadly modifier "manufacturer's" on a warranty; this means
|
||
you have to go back to the equipment's original manufacturer in case
|
||
of problems and can't get satisfaction from the mail-order house.
|
||
Also, manufacturer's warranties run from the date they ship; by the
|
||
time the mail-order house assembles and ships your system, it may
|
||
have run out!
|
||
|
||
Watch for the equally deadly "We do not guarantee compatibility".
|
||
This gotcha on a component vendor's ad means you may not be able to
|
||
return, say, a video card that fails to work with your motherboard.
|
||
|
||
Another dangerous phrase is "We reserve the right to substitute
|
||
equivalent items". This means that instead of getting the
|
||
high-quality name-brand parts advertised in the configuration you
|
||
just ordered, you may get those no-name parts from Upper Baluchistan
|
||
-- theoretically equivalent according to the spec sheets, but perhaps
|
||
more likely to die the day after the warranty expires. Substitution
|
||
can be interpreted as "bait and switch", so most vendors are scared
|
||
of getting called on this. Very few will hold their position if you
|
||
press the matter.
|
||
|
||
Another red flag: "Only warranted in supported environments". This
|
||
may mean they won't honor a warranty on a non-Windows system at all,
|
||
or it may mean they'll insist on installing the Unix on disk
|
||
themselves.
|
||
|
||
One absolute show-stopper is the phrase "All sales are final". This
|
||
means you have no options if a part doesn't work. Avoid any company
|
||
with this policy.
|
||
________________________________________________________________
|
||
|
||
10.2. Special Questions to Ask Web/Mail-Order Vendors Before Buying
|
||
|
||
* Does the vendor have the part or system presently in stock? Mail
|
||
order companies tend to run with very lean inventories; if they
|
||
don't have your item in stock, delivery may take longer. Possibly
|
||
much longer.
|
||
* Does the vendor pay for shipping? What's the delivery wait?
|
||
* If you need to return your system, is there a restocking fee? and
|
||
will the vendor cover the return freight? Knowing the restocking
|
||
fee can be particularly important, as they make keep you from
|
||
getting real satisfaction on a bad major part. Avoid dealing with
|
||
anyone who quotes more than a 15% restocking fee -- and it's a
|
||
good idea, if possible, to avoid any dealer who charges a
|
||
restocking fee at all.
|
||
|
||
Warranties are tricky. There are companies whose warranties are
|
||
invalidated by opening the case. Some of those companies sell
|
||
upgradeable systems, but only authorized service centers can do
|
||
upgrades without invalidating the warranty. Sometimes a system is
|
||
purchased with the warranty already invalidated. There are vendors
|
||
who buy minimal systems and upgrade them with cheap RAM and/or disk
|
||
drives. If the vendor is not an authorized service center, the
|
||
manufacturer's warranty is invalidated. The only recourse in case of
|
||
a problem is the vendor's warranty. So beware!
|
||
________________________________________________________________
|
||
|
||
10.3. Payment Method
|
||
|
||
It's a good idea to pay with AmEx or Visa or MasterCard; that way you
|
||
can stop payment if you get a lemon, and may benefit from a
|
||
buyer-protection plan using the credit card company's clout (not all
|
||
cards offer buyer-protection plans, and some that do have
|
||
restrictions which may be applicable). However, watch for phrases
|
||
like "Credit card surcharges apply" or "All prices reflect 3% cash
|
||
discount" which mean you're going to get socked extra if you pay by
|
||
card.
|
||
|
||
Note that many credit-card companies have clauses in their standard
|
||
contracts forbidding such surcharges. You can (and should) report
|
||
such practices to your credit-card issuer. If you already paid the
|
||
surcharge, they will usually see to it that it is returned to you.
|
||
Credit-card companies will often stop dealing with businesses that
|
||
repeat such behavior.
|
||
________________________________________________________________
|
||
|
||
10.4. Which Clone Vendors to Talk To
|
||
|
||
10.4.1. Some pans
|
||
|
||
Gateway: may also be a vendor to avoid. Apparently their newer
|
||
machines don't have parity bits in their memories; memory is tested
|
||
only on reboot. This is dubious design even for Windows, and totally
|
||
unacceptable for Unix.
|
||
________________________________________________________________
|
||
|
||
10.4.2. Some picks
|
||
|
||
In early August 2001 I designed an `Ultimate Linux Box' with Gary
|
||
Sandine and John Pearson of Los Alamos Computers; you can
|
||
[http://www.catb.org/~esr/writings/ultimate-linux-box/] read all
|
||
about it These guys know what they are doing and are fun to work
|
||
with. If you need a high-end Linux workstation, or your laboratory
|
||
needs a computer cluster, talk with them.
|
||
________________________________________________________________
|
||
|
||
11. After You Take Delivery
|
||
|
||
Your configuration is custom and involves slightly unusual hardware.
|
||
Therefore, keep a copy of the configuration you wrote down, and check
|
||
it against the invoice and the actual delivered hardware. If there is
|
||
a problem, calling back your vendor right away will maximize your
|
||
chances of getting the matter settled quickly.
|
||
________________________________________________________________
|
||
|
||
12. Software to go with your hardware
|
||
|
||
I used to maintain an entire separate FAQ on Unixes for 386/486 and
|
||
Pentium hardware. Times change, industries evolve, and I can now
|
||
replace that FAQ with just three words:
|
||
|
||
Go get Linux!
|
||
|
||
Note
|
||
|
||
FreeBSD or OpenSolaris are currently niche choices, but if they offer
|
||
something you need that Linux doesn't, don't let me stop you from
|
||
trying one or both of them.
|
||
________________________________________________________________
|
||
|
||
13. Other Resources on Building Linux PCs
|
||
|
||
The [http://www.pctechguide.com/] PC Tech Guide offers pretty
|
||
comprehensive descriptions of PC hardware technologies.
|
||
|
||
The Caveat Emptor guide has an especially good section on evaluating
|
||
monitor specifications.
|
||
|
||
Anthony Olszewski's Assembling A PC is an excellent guide to the
|
||
perplexed. Not Linux-specific.
|
||
|
||
Tom's Hardware Guide covers many hardware issues exhaustively. It is
|
||
especially good about CPU chips and motherboards. Full of ads and
|
||
slow-loading graphics, though.
|
||
|
||
The System Optimization Site has many links to other worthwhile sites
|
||
for hardware buyers.
|
||
|
||
Christopher B. Browne has a page on
|
||
[http://linuxfinances.info/info/linuxvars.html#VARS] Linux VARs that
|
||
build systems. He also recommends the Linux VAR HOWTO.
|
||
|
||
There's a Building Your Own PC page. It's more oriented towards
|
||
building from parts than this one. Less technical depth in most
|
||
areas, but better coverage of some including RAM, soundcards and
|
||
motherboard installation. Features nifty and helpful graphics, one of
|
||
the better graphics-intensive pages I've seen. However, the
|
||
hardware-selection advice is out of date.
|
||
|
||
The Linux Hardware Database .
|
||
|
||
The Silent PC Reviews site has lots of good material on building
|
||
quiet PCs.
|