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LDP/howto/docbook/Unix-Hardware-Buyer-HOWTO.xml
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@ -29,9 +29,18 @@ configure generic PC hardware for cheap, powerful Unix systems.
</abstract>
<revhistory>
<revision>
<revnumber>4.0</revnumber>
<date>2007-11-02</date>
<authorinitials>esr</authorinitials>
<revremark>
Major revisions by Jonathan Marsden on SATA, bus standards,
DVDs and other topics, followed by a cleanup pass from me.
</revremark>
</revision>
<revision>
<revnumber>3.3</revnumber>
<date>2007-09-13</date>
<date>2007-18-13</date>
<authorinitials>esr</authorinitials>
<revremark>
Updated for 2007 conditions. CRTs are dead. BTX is
@ -347,12 +356,18 @@ out of the way.</para>
<para>The system bus is what ties all the parts of your machine together.
This is an area in which progress has simplified your choices a lot. There
used to be no fewer than four competing bus standards out there (ISA, EISA,
VESA/VLB, PCI, and PCMCIA). Now there is effectively just one &mdash;PCI-X
used to be no fewer than <emphasis>four</emphasis> competing bus standards
out there (ISA, EISA, VESA/VLB, PCI, and PCMCIA). Now there are
effectively just <emphasis>two</emphasis> &mdash;PCI-X on servers, and PCIe
for desktop/tower machines. Even PCI is now legacy technology, and the
PCMCIA bus that seemed so important a few years back has been reduced to
near-irrelevance by Ethernet and WiFi hardware built onto
motherboards.</para>
near-irrelevance by Ethernet and WiFi hardware built onto motherboards.
The newcomer is PCIe, which is (in late 2007) a
&lsquo;video-card-mostly&rsquo; bus, though it seems to be gaining in
popularity for other uses too on mainstream desktop motherboards, whereas
PCI-X is only found on higher end &lsquo;server&rsquo; motherboards.
</para>
</sect3>
<sect3 id="memory"><title>Memory</title>
@ -367,6 +382,12 @@ types that used to be out there.</para>
machine's bus speed, then buy as much as you can afford to stuff in your
machine.</para>
<note><para>DDR3 RAM is beginning to appear. Right now its extra expense
over DDR2 is not worth paying, for all but extremely specialized needs. It
is almost always <emphasis>far</emphasis> more useful to have 4GB of
reasonably fast RAM, than 2GB of very fast RAM, in your
machine.</para></note>
<para>For more technical stuff on memory architectures, see <ulink
url="http://www.kingston.com/tools/umg/default.asp">The Ultimate Memory
Guide</ulink> maintained by Kingston Technologies.</para>
@ -387,10 +408,10 @@ replaced the older PS/2-style dedicated connector. XFree86 autodetects
your mouse when it starts up, so configuration is not a big deal any
more.</para>
<para>Beware that most PC vendors, being Windows-oriented, bundle
two-button mice. Thus, you may have to buy your own
three-button mouse. Ignore the adspeak about dpi and pick a
mouse or trackball that feels good to your hand.</para>
<para>Some PC vendors, being Windows-oriented, still bundle two-button
mice. Thus, you may have to buy your own three-button (or two button and a
scroll wheel) mouse. Ignore the adspeak about dpi and pick a mouse or
trackball that feels good to your hand.</para>
<para>Your humble editor really, really likes the Logitech TrackMarble, an
optical trackball that eliminates the chronic roller-fouling problems of
@ -400,11 +421,11 @@ accept them.</para>
</sect3>
<sect3 id="floppies"><title>Floppy Drives</title>
<para>There's no longer much to be said about floppy drives. They're cheap,
they're generic, and the rise of CD-ROM drives as a cheap distribution
medium has made them much less important than formerly. You only ever see
the 3.5-inch &lsquo;hard-shell&rsquo; floppies with 1.44MB capacity
anymore.</para>
<para>There's no longer much to be said about floppy drives. They're
cheap, they're generic, and the rise of CD-ROM and DVD-ROM drives as a
cheap distribution medium has made them much less important than formerly.
You only ever see the 3.5-inch &lsquo;hard-shell&rsquo; floppies with
1.44MB capacity anymore.</para>
<para>Bootable CD-ROMs killed off the last use of floppies, which was OS
installation. So go ahead and settle for cheap Mitsumi and Teac floppy
@ -423,7 +444,7 @@ on ISO-9660 CD-ROM, a cheaper and better method than the QIC tapes we used
to use.</para>
<para>CD-ROM speed used to be a big deal; vendors advertised 2X, 4X, all
the way up to 40X. Vendors don't bother any more; the drives are all about
the way up to 52X. Vendors don't bother any more; the drives are all about
equivalently fast now.</para>
<para>There are one or two minor features to watch for. Most CD-ROMS will
@ -432,28 +453,36 @@ ones will also include two RCA jacks for use with speakers. Another
feature to look for is a drive door or seal that protects the drive head
from dust.</para>
<para>Increasingly, DVD-ROM drives (and burners) are replacing CD-ROM drives
as the default optical drive in PC systems. They have significantly larger
capacity, and will read (and burn) CD media too. The cost difference now
is so small that it is usually preferable to buy a DVD burner instead of
a CD-ROM drive.</para>
</sect3>
<sect3 id="backup"><title>Backup devices</title>
<para>It's good to be able to make backups that you can separate from your
system and store off-site in case of disaster. Until recently, tape drives
still seemed like a good idea for personal systems, but I found I seldom
used mine. Today, tape drive with high enough capacity to image today's
huge hard disks are too expensive to make sense any more.</para>
system and store off-site in case of disaster. Until about 2001, tape
drives still seemed like a good idea for personal systems, but I found I
seldom used mine. Today, tape drive with high enough capacity to image
today's huge hard disks are too expensive to make sense any more.</para>
<para>For the money you'd spend on a high-capacity tape drive (over
$1000) it makes more sense to buy a laptop and a pile of CD-RW media. Sit
the laptop on your house Ethernet when you're not traveling, and back up
the main machine to it every day, or oftener. Between the efficiency of
rsync and the speed of 100-megabit Ethernet, this will be a lot faster than
making a tape. Every once in a while, burn a set of backup CD-ROMs.</para>
<para>For the money you'd spend on a high-capacity tape drive (over $1000)
it makes more sense to buy a laptop and a pile of CD-R or DVD-R or DVD+R
media. Sit the laptop on your house Ethernet when you're not traveling, and
back up the main machine to it every day, or oftener. Between the
efficiency of rsync and the speed of 100-megabit Ethernet, this will be a
lot faster than making a tape. Every once in a while, burn a set of backup
CD-ROMs or DVDROMs.</para>
<para>But CD-ROMs aren't reusable; the cost piles up over time. An
interesting alternative is a small external USB hard drive, especially if
you can salvage an old laptop drive and put it in a USB enclosure. These
enclosures are available for about $30; Google for "USB HD
Enclosure". This is faster than a tape, cheaper and lighter than a
full laptop.</para>
enclosures are available for about $30; Google for "USB HD Enclosure". This
is faster than a tape, cheaper and lighter than a full laptop. For faster
transfer speeds, an enclosure that accepts eSATA connections as well as USB
helps a lot (assuming your PC or notebook has an eSATA connector).</para>
</sect3>
</sect2>
@ -476,14 +505,26 @@ AMD chips still deliver more performance than you're likely to be able
to use and do it with lower power dissipation (thus, less noise and
heat).</para>
<para>To compare the performance of different Intel-based systems with
each other and with machines from other manufacturers, you can take a
look at the SPECmark Table at <ulink
url="ftp://ftp.cdf.toronto.edu/pub/spectable">ftp://ftp.cdf.toronto.edu/pub/spectable</ulink>.
That document recommends (and I do too) that you read the SPEC FAQ at
<ulink
url="http://www.specbench.org/spec/faq">http://www.specbench.org/spec/specfaq.html</ulink>
to get background before browsing the table.</para>
<para>Many CPUs now are multi-core &mdash; that is, they have multiple CPUs
on a single chip. This is very useful for doing something compute
intensive (re-encoding video, compressing large archives, etc.) in the
background and still having a responsive system for other work at the same
time. At current prices, a dual-core CPU makes good sense for most desktop
systems. If you are creating a server or have specialized computing needs
you expect to be very CPU-intensive, quad-core is worth considering. Only
at the very low end (sub US$50 CPUs) do single-core CPUs still make sense
on desktop machines.</para>
<para>Mainstream desktop CPUs now use one of two sockets: LGA 775 (Intel)
and AM2 (AMD). Buying a system that uses one of these stands more chance
of allowing a useful CPU upgrade to extend its useful life than systems
using other less common sockets.</para>
<para>Current CPUs are <emphasis>much</emphasis> faster than those of just
a few years ago. As a result, unless your needs are highly specialized,
spending more than about US$200 on a desktop CPU is hard to justify.
Putting extra budget into more RAM or a faster disk subsystem will most
likely result in greater benefit to most users.</para>
</sect2>
@ -505,8 +546,18 @@ your home disk; in that case, you can still run and do recovery stuff and
basic Net communications until you can buy another home disk and restore it
from backups (you <emphasis>did</emphasis> keep backups, right?).</para>
<para>Your performance-tuning choice is IDE versus SCSI. We'll have more
to say about that in <xref linkend='optimize'/>.</para>
<para>Given today's high capacity drives, another way to use two disks well
is to set them up as a RAID1 (mirrored) array. This can be done in
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
<emphasis>do</emphasis> fail, so this approach (as well as good backups) is
well worth considering.</para>
<para>Your performance-tuning choice is SATA versus SCSI (the older IDE and
EIDE buses are now obsolete). We'll have more to say about that in <xref
linkend='optimize'/>.</para>
</sect2>
<sect2 id="cases"><title>Getting Down to Cases</title>
@ -524,7 +575,7 @@ throughout. </para>
heat better.</para></listitem>
<listitem><para>Unobstructed air intake with at least one fan each
(in addition to the power supply and processor fans)</para></listitem>
<listitem><para>No sharp metal edges. You doon't want to shred
<listitem><para>No sharp metal edges. You don't want to shred
your hands when you're tinkering with things.</para></listitem>
<listitem><para>There shouldn't be any hot spots (poor air flow).</para></listitem>
<listitem><para>Sturdy card clips. Some poorly-designed cases allow cards
@ -666,20 +717,22 @@ hardware." on this list. But processors run so hot nowadays that all
current motherboards have it.)</para>
<para>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.</para>
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 <ulink
url="http://www.dtxpc.org/">DTX</ulink> specification for small-form-factor
PCs; it remains to be seen whether this will gain any traction.</para>
</sect2>
<sect2><title>Monitor and Video</title>
<para>The largest user-visible change since the last 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 now (late 2007)
becoming generally available at reasonable prives even that reason is gone.
It's all flatscreens now, baby.</para>
<para>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 now
(late 2007) becoming generally available at reasonable prives even that
reason is gone. It's all flatscreens now, baby.</para>
<para>On flatscreens, only two statistics matter; pixel size and response
time. The biggest functional drawback of flatscreens relative to CRTs is
@ -692,8 +745,9 @@ may be worth it.</para>
<para>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 it's simple; all
cards have enough display memory for every resolution in use, and 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?)</para>
@ -708,14 +762,26 @@ interlacing, and flicker. That stuff is all obsolete now.</para>
<para>Here's what to look for on the monitor spec sheet:</para>
<itemizedlist>
<listitem><para>Dot pitch of 0.28 or smaller on a 12&quot;-15&quot;
monitor; 0.30 is acceptable on larger ones, especially 19&quot; to 21&quot;
screens. Dot pitch is the physical resolution of the screen's phosphor
mask. Larger dot pitches mean that small fonts and graphic details will be
fuzzy.</para></listitem>
<itemizedlist> <listitem><para>Screen size and format. Usually measured in
diagonal inches. Many screens are now in a <quote>widescreen</quote>
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 <quote>19
inch</quote> widescreen monitor generally has considerably fewer pixels
than a <quote>19 inch</quote> 5:4 ratio one.</para></listitem>
<listitem><para>5ms or lower response time. 3ms is better.</para></listitem>
<listitem><para>Screen resolution. 1280x1024 is now low end on the
desktop. Seventeen inch 1280x1024 screens are the bargain basement now,
some manufacturers already switching production to 19 inch widescreen
1440x900 screens instead. In late 2007, 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.</para></listitem>
<listitem><para>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.</para></listitem>
<listitem><para>Does it have a tilt-and-swivel base? Adequate
controls, including both horizontal and vertical size and horizontal
@ -732,8 +798,32 @@ brands) even among monitors of the same make and model.</para>
</sect2>
<sect2 id="dvd"><title>DVD Drives</title>
<para>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).</para>
<sect3 id="dvd_data_storage"><title>DVDs for Data Storage</title>
<para>DVD burners (drives that can read and write CDROM media as well as
several kinds of DVD media) are now low cost and useful. Most come with
either a parallel ATA ("IDE") interface or, increasingly, a SATA interface.
Linux and most current PC Unix-like systems will work fine with either
interface. Given the choice, SATA is slightly preferable because the cable
is smaller and simpler, and modern motherboards have more SATA connections
than parallel ATA ones.</para>
<para>There is probably little or no benefit in seeking out a DVD
drive with a SCSI interface any longer.</para>
</sect3>
<sect3 id="dvd_video"><title>DVDs for Video Playback</title>
<para>(Most of this section courtesy of James Turinsky.)</para>
<para>If you only need to watch video DVDs sold for and intended to be
played in your own "region" of the world, you may skip this section.</para>
<para>Most drives manufactured after January 1st 2000, and some drives prior
to that have come installed with something called RPC2.</para>
@ -771,6 +861,8 @@ wish to buy.</para>
<para>For more, see the <ulink url="http://forum.rpc1.org/portal.php">Firmware
Patches</ulink> site.</para>
</sect3>
</sect2>
<sect2 id="sound"><title>Sound Cards and Speakers</title>
@ -790,11 +882,25 @@ these days support support all these features:</para>
<listitem><para>A microphone jack for sound input.</para></listitem>
</itemizedlist>
<para>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, almost anything will work fine!</para>
<para>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 <ulink
url="http://www.alsa-project.org/main/index.php/Matrix:Main">ALSA Sound
Card Matrix</ulink>.</para>
<para>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 <quote>self-powered</quote>, 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.</para>
bass and treble controls. Some speakers run off the card's 4-watt signal;
others are <quote>self-powered</quote>, 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.</para>
<para>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
@ -805,11 +911,11 @@ accept the audio cable connector.</para>
</sect2>
<sect2 id="modems"><title>Modems</title>
<para>Demand for 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.</para>
<para>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.</para>
<para>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
@ -817,6 +923,13 @@ 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).</para>
<note><para>If you live somewhere with <emphasis>really</emphasis> 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
<ulink url="http://www.usrobotics.com">U.S. Robotics</ulink> web site for
current product numbers and more detailed specifications.</para></note>
<para>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
@ -835,11 +948,11 @@ adding a new protocol is basically a software change.</para>
<sect3 id="modem_format"><title>Internal vs. External</title>
<para>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 port to connect your external modem to.</para>
<para>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.</para>
<para>Pay that premium &mdash; being able to see the blinkenlights on
the external ones will help you understand and recover from
@ -874,18 +987,18 @@ 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). </para>
<para>Many fax 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 &mdash;
it's cheaper, and lowers the likelihood that something vital to your
communications needs has been left out of the hardware.</para>
</sect3>
<sect3><title>Fax Modems</title>
<para>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 &mdash; it's cheaper,
and lowers the likelihood that something vital to your communications needs
has been left out of the hardware.</para>
<para>Avoid <quote>Class 1</quote> and <quote>Class 2</quote> modems. Look
for <quote>Class 2.0</quote> for the full EIA-standard command set.</para>
</sect3>
<sect3><title>Fax Modems</title>
<para>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:</para>
@ -977,7 +1090,18 @@ PostScript files to a copy shop...)</para>
<para>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 may be obsolete soon.</para>
Parallel ports (and serial ports for that matter) are becoming obsolete.
Many new PC motherboards no longer include them.</para>
<para>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.</para>
<para>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.</para>
</sect2>
<sect2 id="power_protection"><title>Power Protection</title>
@ -1092,7 +1216,7 @@ away SCSI for SATA your reliability (expected time before failure) will
drop. We'll cover this in more detail in the next section.</para>
</sect2>
<sect2 id="diskwars"><title>Disk Wars: IDE vs. SCSI</title>
<sect2 id="diskwars"><title>Disk Wars: SATA vs. SCSI</title>
<para>For the fastest disks you can find, pay close attention to
average seek and latency time. The former is an average time
@ -1131,11 +1255,11 @@ constraint in drive design.</para>
are obsolete). Either kind of disk costs about the same, but the premium
for a SCSI card varies all over the lot, partly because of price
differences between VLB and PCI SCSI cards and especially because many
motherboard vendors bundle an IDE chipset right on the system board. SCSI
motherboard vendors bundle a SATA chipset right on the system board. SCSI
gives you better speed and throughput and loads the processor less, a win
for larger disks and an especially significant consideration in a
multi-user environment; also it's more expandable. You can have at most two
IDE devices; four for EIDE. SCSI permits up to 7 (15 for wide
multi-user environment; also it's more expandable. You can have at most four
SATA devices on a single controller. SCSI permits up to 7 (15 for wide
SCSI).</para>
<para>Admittedly, the case for SCSI has eroded a bit since 2001; the new
@ -1153,52 +1277,10 @@ cabling most vendors ship can be flaky. You have to use expensive
high-class cables for consistently good results. See <link
linkend="sutton">Mark Sutton's horror story</link>.</para>
<sect3><title>Enhanced IDE</title>
<para>These days you seldom see plain IDE; souped-up variants are more
usual. These are "Enhanced IDE" (E-IDE) and "Fast AT Attachment" (usually
ATA for short). ATA is Seagate's subset of E-IDE, excluding some features
designed to permit chaining with CD-ROMs and tape drives using the "ATAPI"
interface (an E-IDE extension); in practice, ATA and E-IDE are
identical.</para>
<para>You'll need to be careful about chaining in CD-ROMs and tape
drives when using IDE/ATA. The IDE bus sends all commands to all
disks; they're supposed to latch, and each drive then checks to see
whether it is the intended target. The problem is that badly-written
drivers for CD-ROMs and tapes can collide with the disk command set.
It takes expertise to match these peripherals.</para>
<para>Neither ATA nor E-IDE has the sustained throughput capacity of
SCSI (they're not designed to) but they are 60-90% faster than plain
old IDE. E-IDE's new <quote>mode 3</quote> boosts the IDE transfer rate from
IDE's 3.3MB/sec to 13.3MB/sec. The new interface supports up to 4
drives of up to 8.4 gigabytes capacity.</para>
<para>E-IDE and ATA are advertised as being completely compatible with
old IDE. Theoretically, you can mix IDE, E-IDE and ATA drives and
controllers any way you like, and the worst result you'll get is
conventional IDE performance if the enhancements don't match up (the
controller picks the lowest latch speed). In practice, some IDE
controllers (notably the BusLogic) choke on enhanced IDE.</para>
<para>Accordingly, I recommend against trying to mix device types an
an E-IDE/ATA bus. Unfortunately, this removes much of E-IDE/ATA's
usefulness!</para>
<para>E-IDE on drives above 540MB does automatic block mapping to fool the
BIOS about the drive geometry (avoiding limits in the BIOS type tables).
They don't require special Unix drivers.</para>
<para>Many motherboards now support <quote>dual EIDE</quote> channels,
i.e. two separate [E]IDE interfaces each of which can, theoretically,
support two IDE disks or ATA-style devices.</para>
</sect3>
<sect3><title>Advantages of SCSI</title>
<para>For starters, SCSI is still at least 10%-15% faster than IDE/ATAPI
running flat out. Like Windows, SATA Iis layered over a pile of ancestral
running flat out. Like Windows, SATA I is layered over a pile of ancestral
designs (ST-506 and IDE) that's antiquated and prone to failure under
stress. For example, on the Tyan K7 motherboards, there are known
data-corruption problems with the ATA controller in the presence of various
@ -1219,7 +1301,7 @@ implements. With disconnect/reconnect, if a target device has to perform
some kind of time-consuming mechanical operation (e.g., a seek in the case
of a disk or a medium position operation in the case of a tape drive) the
device will release control of the SCSI bus and allow it to be used for
some other operation.IDE/ATAPI has no such capability and is often
some other operation. IDE/ATAPI has no such capability and is often
responsible for a system stall while a disk, CD-drive or tape drive seeks
to the desired medium position.</para>
@ -1422,36 +1504,14 @@ or a thumbwheel.</para>
<para>SCSI IDs are completely independent of physical device chain
position.</para>
<para>Heuristic 1: If you're buying narrow SCSI, stick with controllers and
devices that use the Centronics-style 50-pin connector. Internally these
connectors are physically identical to diskette cables. Externally they
use a D50 shell. This "standard" connector is common in the
desktop/tower/rackmount-PC world, but you'll find lots of funky DIN and
mini-DIN plugs on devices designed for Macintosh boxes and some laptops.
Ask in advance and don't get burned.</para>
<para>Heuristic 2: For now, when buying a controller, go with an Adaptec
xx42 or one of its clones such as the BusLogic 542. (I like the
BusLogic 946 and 956, two particularly fast Adaptec clones
well-supported under Linux.) The Adaptec is the card everybody
supports and the de-facto standard. Occasional integration problems
have been reported with Unix under Future Domain and UltraStor cards,
apparently due to command-set incompatibilities. At least, before you
buy these, make sure your OS explicitly supports them. </para>
<para>However: Beware the combination of an Adaptec 1542 with a PCI Mach32
video card. Older (1.1) Linux kernels handled it OK, but all current ones
choke. Your editor had to replace his 1542 because of this, swearing
sulphurously the while. </para>
<para>Heuristic 3: You'll have fewer hassles if all your cables are made by
<para>Heuristic A: You'll have fewer hassles if all your cables are made by
the same outfit. (This is due to impedence reflections from minor
mismatches. You can get situations where cable A will work with B,
cable B will work with C, but A and C aren't happy together. It's
also non-commutative. The fact that `computer to A to B' works
doesn't mean that `computer to B to A' will work.</para>
<para id="sutton">Heuristic 4. Beware Cheap SCSI Cables!</para>
<para id="sutton">Heuristic B. Beware Cheap SCSI Cables!</para>
<para>Mark Sutton tells the following instructive horror story in a
note dated 5 Apr 1997: </para>
@ -1539,20 +1599,20 @@ to reflect more recent developments.)</emphasis></para>
piece without benefit, and <emphasis>construct the whole pipe such that
it can feed what your OS/application combo needs</emphasis>.</para>
<para>It's important to recognize that <quote>balance</quote> 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 <quote>big boys</quote> 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.</para>
<para>It's important to recognize that <quote>balance</quote> 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 <quote>big boys</quote> 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.</para>
<para>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
@ -1804,8 +1864,10 @@ here. :-)</para>
levels lower than commercial state of the art.</para></listitem>
</itemizedlist>
<para>For best value, look in the <emphasis>middle</emphasis> of the current
range of available processors.</para>
<para>For best value, look in the <emphasis>middle</emphasis> 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!</para>
<para>Why? Because of the way manufacturers' price-performance curves are
shaped. The top-of-line system is generally boob bait for corporate
@ -1829,6 +1891,11 @@ sickeningly.</para>
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.</para>
<para>Consider SATA hard drives instea of SCSI. Consider one drive rather
than two. This <emphasis>will</emphasis> reduce overall system performance
somewhat, but the cost saving as a fraction of total system cost is often
substantial.</para>
<para>Another easy economy measure is looking for repaired or reconditioned
parts with a warranty. These are often as good as new, and much
cheaper.</para>
@ -1838,6 +1905,10 @@ cheaper.</para>
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 &mdash; it
will be worth it.</para>
<para>Similarly, do not reduce the amount of RAM in your system too far. A
minimum of 2GB of RAM is helpful in desktop systems today.</para>
</sect1>
<sect1 id='noise'><title>Noise Control and Heat Dissipation</title>
@ -2065,11 +2136,14 @@ 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.</para>
<para>Second: with present flatscreens, 1024x768 color is the best you're
going to do (though that may change soon). 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).</para>
<para>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).</para>
<para>Third: about those vendor-supplied time-between-recharge
figures; <emphasis>don't believe them</emphasis>. They collect those
@ -2077,6 +2151,16 @@ 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.</para>
<para>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.</para>
</sect1>
<sect1 id="howtobuy"><title>How to Buy</title>
@ -2136,10 +2220,11 @@ The minor one is computer fairs.</para>
<para>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.
If you still have one in your neighborhood, you're lucky. 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.)</para>
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.)</para>
<para>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
@ -2203,6 +2288,10 @@ 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.)</para>
<para>Note, however: <emphasis>Avoid Best Buy</emphasis>. Horror stories
about them are legion &mdash; predatory salescritters, incompetent
service, routine bait-and-switch tactics.</para>
<para>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
@ -2442,6 +2531,10 @@ replace that FAQ with just three words:</para>
<para><emphasis role="strong">Go get Linux!</emphasis></para>
<note><para>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.</para></note>
</sect1>
<sect1 id="links"><title>Other Resources on Building Linux PCs</title>
@ -2496,3 +2589,4 @@ fill-column:75
compile-command: "mail -s \"Unix Hardware Buyer HOWTO update\" submit@en.tldp.org <Unix-Hardware-Buyer-HOWTO.xml"
End:
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