1318 lines
43 KiB
HTML
1318 lines
43 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML
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><HEAD
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><TITLE
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>Buying the Basics</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="The Unix Hardware Buyer HOWTO"
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HREF="index.html"><LINK
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REL="PREVIOUS"
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TITLE="Overview of the Market"
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HREF="overview.html"><LINK
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TITLE="What To Optimize"
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HREF="optimize.html"></HEAD
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>The Unix Hardware Buyer HOWTO</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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HREF="overview.html"
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ACCESSKEY="P"
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>Prev</A
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VALIGN="bottom"
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><TD
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ALIGN="right"
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VALIGN="bottom"
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HREF="optimize.html"
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>Next</A
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="sect1"
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><H1
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CLASS="sect1"
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><A
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NAME="basics"
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></A
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>3. Buying the Basics</H1
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><P
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>In this section, we cover things to look out for that are more or less
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independent of price-performance tradeoffs, part of your minimum system
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for running Unix.</P
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><P
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>Issues like your choice of disk, processor, and I/O bus (where there is
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a significant tradeoff between price and capability) are covered in the section
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on <A
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HREF="optimize.html"
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>What To Optimize</A
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>.</P
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><DIV
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CLASS="sect2"
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><H2
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CLASS="sect2"
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><A
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NAME="AEN132"
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></A
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>3.1. Things to Not Care About</H2
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><P
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>An effect of PC commoditization is that there aren lots of things
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you used to have to worry about that don't matter any more, because
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the market has completely flattened out. We list these here to get them
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out of the way.</P
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><DIV
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CLASS="sect3"
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><H3
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CLASS="sect3"
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><A
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NAME="buswars"
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></A
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>3.1.1. Bus Wars</H3
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><P
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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. There
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used to be no fewer than <EM
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>four</EM
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> competing bus standards
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out there (ISA, EISA, VESA/VLB, PCI, and PCMCIA). Now there are
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effectively just <EM
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>two</EM
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> —PCI-X on servers, and PCIe
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for desktop/tower machines. Even PCI is now legacy technology, and the
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PCMCIA bus that seemed so important a few years back has been reduced to
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near-irrelevance by Ethernet, USB, and WiFi hardware built onto
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motherboards. The newcomer is PCIe, which is (in late 2007) a
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‘video-card-mostly’ bus, though it seems to be gaining in
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popularity for other uses too on mainstream desktop motherboards, whereas
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PCI-X is only found on higher end ‘server’ motherboards.
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</P
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></DIV
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><DIV
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CLASS="sect3"
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><H3
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CLASS="sect3"
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><A
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NAME="memory"
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></A
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>3.1.2. Memory</H3
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><P
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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 baked
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into the processor itself now. This removed a large source of latency and
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design variations. It also killed off the plethora of different RAM
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types that used to be out there.</P
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><P
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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 your
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machine.</P
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><DIV
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CLASS="note"
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><P
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></P
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><TABLE
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CLASS="note"
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WIDTH="100%"
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BORDER="0"
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><TR
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><TD
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WIDTH="25"
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ALIGN="CENTER"
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VALIGN="TOP"
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><IMG
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SRC="../images/note.gif"
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HSPACE="5"
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ALT="Note"></TD
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><TD
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ALIGN="LEFT"
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VALIGN="TOP"
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><P
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>DDR3 RAM is beginning to appear. Right now its extra expense
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over DDR2 is not worth paying, for all but extremely specialized needs. It
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is almost always <EM
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>far</EM
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> more useful to have 4GB of
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reasonably fast RAM, than 2GB of very fast RAM, in your
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machine.</P
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></TD
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></TR
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></TABLE
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></DIV
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><P
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>For more technical stuff on memory architectures, see <A
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HREF="http://www.kingston.com/tools/umg/default.asp"
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TARGET="_top"
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>The Ultimate Memory
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Guide</A
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> maintained by Kingston Technologies.</P
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></DIV
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><DIV
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CLASS="sect3"
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><H3
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CLASS="sect3"
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><A
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NAME="mice"
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></A
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>3.1.3. Keyboards and Mice</H3
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><P
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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 <SPAN
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CLASS="QUOTE"
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>"Internet"</SPAN
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> buttons on it;
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this is 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
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just fine.</P
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><P
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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 autodetects
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your mouse when it starts up, so configuration is not a big deal any
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more.</P
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><P
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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 and a
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scroll wheel) mouse. Ignore the adspeak about dpi and pick a mouse or
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trackball that feels good to your hand.</P
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><P
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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 of
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the older TrackMan. They're well-supported by X, so any Linux or BSD will
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accept them.</P
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></DIV
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><DIV
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CLASS="sect3"
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><H3
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CLASS="sect3"
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><A
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NAME="floppies"
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></A
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>3.1.4. Floppy Drives</H3
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><P
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>There's no longer much to be said about floppy drives. They're
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cheap, they're generic, and the rise of CD-ROM and DVD-ROM drives as a
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cheap 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
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1.44MB capacity anymore.</P
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><P
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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 floppy
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drives. There are no ‘premium’ floppy drives anymore. Nobody
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bothers.</P
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><P
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>It's possible your system won't even include one. No loss.</P
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></DIV
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><DIV
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CLASS="sect3"
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><H3
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CLASS="sect3"
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><A
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NAME="cdrom"
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></A
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>3.1.5. CD-ROM Drives</H3
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><P
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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 <SPAN
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CLASS="QUOTE"
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>"High Sierra"</SPAN
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>). All current
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Unixes support these devices. Unix and Linux software is now distributed
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on ISO-9660 CD-ROM, a cheaper and better method than the QIC tapes we used
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to use.</P
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><P
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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 about
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equivalently fast now.</P
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><P
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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. Better-quality
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ones will also include two RCA jacks for use with speakers. Another
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feature to look for is a drive door or seal that protects the drive head
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from dust.</P
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><P
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>Increasingly, DVD-ROM drives (and burners) are replacing CD-ROM drives
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as the default optical drive in PC systems. They have significantly larger
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capacity, and will read (and burn) CD media too. The cost difference now
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is so small that it is usually preferable to buy a DVD burner instead of
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a CD-ROM drive.</P
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></DIV
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><DIV
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CLASS="sect3"
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><H3
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CLASS="sect3"
|
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><A
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NAME="backup"
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></A
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>3.1.6. Backup devices</H3
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><P
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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 found I
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seldom used mine. Today, tape drives with high enough capacity to image
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today's huge hard disks are too expensive to make sense any more.</P
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><P
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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 DVD+R
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media. Sit the laptop on your house Ethernet when you're not traveling, and
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back up the main machine to it every day, or oftener. Between the
|
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efficiency of rsync and the speed of 100-megabit Ethernet, this will be a
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lot faster than making a tape. Every once in a while, burn a set of backup
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CD-ROMs or DVDROMs.</P
|
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><P
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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, especially if
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you can salvage an old laptop drive and put it in a USB enclosure. These
|
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enclosures are available for about $30; Google for "USB HD Enclosure". This
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is faster than a tape, cheaper and lighter than a full laptop. For faster
|
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transfer speeds, an enclosure that accepts eSATA connections as well as USB
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helps a lot (assuming your PC or notebook has an eSATA connector).</P
|
|
></DIV
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></DIV
|
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><DIV
|
|
CLASS="sect2"
|
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><H2
|
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CLASS="sect2"
|
|
><A
|
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NAME="processor"
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></A
|
|
>3.2. How To Pick Your Processor</H2
|
|
><P
|
|
>Right now (early 2010), the chips to consider for running Unix are
|
|
the the 64-bit AMD Opteron or its Intel equivalents, especially the Core 2
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Duo. We're long past the point at which 32-bit chips are interesting for
|
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new desktop systems, presuming you could even find one. AMD and Intel built
|
|
up a buffer before switching their fabs fully to 64-bit chips in 2006, and
|
|
the 32-bit chips you can still find are coming out of warehouses rather
|
|
than off production lines.</P
|
|
><P
|
|
>Brands don't matter much, so don't feel you need to pay Intel's
|
|
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
|
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the AMD line. They used to be faster, cheaper, and better-designed than
|
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Intel processors; today Intel has clawed back the speed advantage, but
|
|
AMD chips still deliver more performance than you're likely to be able
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to use and do it with lower power dissipation (thus, less noise and
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heat).</P
|
|
><P
|
|
>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 fully
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open-source drivers. This will avoid the problems you would otherwise face
|
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trying to select a supported graphics card from ATI or Nvidia.</P
|
|
><P
|
|
>Many CPUs now are multi-core — that is, they have multiple CPUs
|
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on a single chip. This is very useful for doing something compute
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intensive (re-encoding video, compressing large archives, etc.) in the
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|
background and still having a responsive system for other work at the same
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time. At current prices, a dual-core CPU makes good sense for most desktop
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systems. If you are building a server or have specialized computing needs
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you expect to be very CPU-intensive quad-core is worth considering, but on
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a desktop system all the two extra cores will usually do is emit heat. Only
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at the very low end (sub US$50 CPUs) do single-core CPUs still make sense
|
|
on desktop machines.</P
|
|
><P
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|
>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.</P
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|
><P
|
|
>Current CPUs are <EM
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|
>much</EM
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|
> faster than those of just
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a few years ago. As a result, unless your needs are highly specialized,
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spending more than about US$200 on a desktop CPU is hard to justify. For
|
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most users, putting extra budget into more RAM or a faster disk subsystem
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will most likely result in greater benefit.</P
|
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></DIV
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><DIV
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CLASS="sect2"
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><H2
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CLASS="sect2"
|
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><A
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NAME="twospindles"
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></A
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|
>3.3. One Disk or Two?</H2
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><P
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|
>I usually build with two disks — one <SPAN
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CLASS="QUOTE"
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>"system"</SPAN
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> disk
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and one <SPAN
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CLASS="QUOTE"
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>"home"</SPAN
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> disk. There are two good reasons to do this
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that have nothing to do with the extra capacity. One of them is the
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performance advantage of being able to interleave commands to different
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physical spindles that we'll explain a bit later in the section on disks.
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The other is that I am quite a bit less likely to lose two disks at once
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than I am to trash a single one.</P
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><P
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|
>Let's suppose you have a fatal disk crash. If you have only one
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disk, 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 new
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Linux installation knowing your personal files are safe. Or maybe it was
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your home disk; in that case, you can still run and do recovery stuff and
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basic Net communications until you can buy another home disk and restore it
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from backups (you <EM
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|
>did</EM
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> keep backups, right?).</P
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><P
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|
>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
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drives fail, the system will continue to function, no data is lost, and
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upon replacing the failed drive, the array can be rebuilt from the
|
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remaining working drive. Hard drives are consumable media, they
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<EM
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|
>do</EM
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> fail, so this approach (as well as good backups) is
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well worth considering.</P
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><P
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|
>Buy SATA. The older IDE and EIDE buses are now obsolete, and SCSI no
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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.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="cases"
|
|
></A
|
|
>3.4. Getting Down to Cases</H2
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|
><P
|
|
>I used to say that cases are just bent metal, and that it doesn't
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|
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
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|
concern. They need to be well designed for proper airflow
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|
throughout. </P
|
|
><P
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|
>Look for the following quality features:</P
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><P
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|
></P
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><UL
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><LI
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|
><P
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|
>Aluminum rather than steel. It's lighter and conducts
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|
heat better.</P
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></LI
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|
><LI
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|
><P
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|
>Unobstructed air intake with at least one fan each
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(in addition to the power supply and processor fans)</P
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|
></LI
|
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><LI
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|
><P
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|
>No sharp metal edges. You don't want to shred
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|
your hands when you're tinkering with things.</P
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|
></LI
|
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><LI
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|
><P
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|
>There shouldn't be any hot spots (poor air flow).</P
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|
></LI
|
|
><LI
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|
><P
|
|
>Sturdy card clips. Some poorly-designed cases allow cards
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|
to wiggle out of their slots under normal vibration.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Effective and easy to use mechanisms for attaching hard
|
|
drives, CD-ROM, CD-R/W, DVDs, etc.</P
|
|
></LI
|
|
></UL
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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
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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
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get for that is less desktop clutter, more and bigger bays for expansion,
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and often (perhaps most importantly) a beefed-up power-supply and fan.
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Putting the box and its fan under a table is good for maybe 5db off the
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effective noise level, too. Airflow is also an issue; if the peripheral
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bays are less cramped, you get better cooling. Be prepared to buy
|
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extension cables for your keyboard and monitor, though; vendors almost
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|
never include enough flex.</P
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|
><P
|
|
>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,
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|
will fit into a baby or midsized tower with ample room for expansion;
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|
and the whole thing will fit under a desk and make less noise than a
|
|
classic tower.</P
|
|
><P
|
|
>For users with really heavy expandability requirements,
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|
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
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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.</P
|
|
><P
|
|
>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.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="power"
|
|
></A
|
|
>3.5. Power Supplies and Fans</H2
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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).</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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
|
|
<A
|
|
HREF="http://www.papstplc.com/"
|
|
TARGET="_top"
|
|
>Papst</A
|
|
>.
|
|
</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="motherboards"
|
|
></A
|
|
>3.6. Motherboards</H2
|
|
><P
|
|
>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
|
|
<SPAN
|
|
CLASS="QUOTE"
|
|
>"name"</SPAN
|
|
> 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.</P
|
|
><P
|
|
>Some good features to look for in a motherboard include:</P
|
|
><P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
>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!)</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>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.</P
|
|
></LI
|
|
></UL
|
|
><P
|
|
>(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.)</P
|
|
><P
|
|
>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 <A
|
|
HREF="http://www.dtxpc.org/"
|
|
TARGET="_top"
|
|
>DTX</A
|
|
> specification for small-form-factor
|
|
PCs; it seems also to have sunk without trace.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="AEN238"
|
|
></A
|
|
>3.7. Monitor and Video</H2
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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?)</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>I used to carry a lot of material on different video standards,
|
|
interlacing, and flicker. That stuff is all obsolete now.</P
|
|
><P
|
|
>Here's what to look for on the monitor spec sheet:</P
|
|
><P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
>Screen size and format. Usually measured in
|
|
diagonal inches. Most displays are now in a <SPAN
|
|
CLASS="QUOTE"
|
|
>"widescreen"</SPAN
|
|
>
|
|
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 <SPAN
|
|
CLASS="QUOTE"
|
|
>"19
|
|
inch"</SPAN
|
|
> widescreen monitor generally has considerably fewer pixels
|
|
than a <SPAN
|
|
CLASS="QUOTE"
|
|
>"19 inch"</SPAN
|
|
> 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.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>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.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>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.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>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.</P
|
|
></LI
|
|
></UL
|
|
><P
|
|
>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.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="dvd"
|
|
></A
|
|
>3.8. DVD Drives</H2
|
|
><P
|
|
>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).</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="sound"
|
|
></A
|
|
>3.9. Sound Cards and Speakers</H2
|
|
><P
|
|
>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:</P
|
|
><P
|
|
></P
|
|
><UL
|
|
><LI
|
|
><P
|
|
>16-bit sampling (for 65536 dynamic levels rather
|
|
than 256).</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Mono and stereo support.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Full-duplex mode.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>Sampling rate of 44.1KHz (CD-quality).</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>MIDI interface via a standard 15-pin D-shell
|
|
connector.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>RCA output jacks for headphones or speakers.</P
|
|
></LI
|
|
><LI
|
|
><P
|
|
>A microphone jack for sound input.</P
|
|
></LI
|
|
></UL
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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 <A
|
|
HREF="http://www.alsa-project.org/main/index.php/Matrix:Main"
|
|
TARGET="_top"
|
|
>ALSA Sound
|
|
Card Matrix</A
|
|
>.</P
|
|
><P
|
|
>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 <SPAN
|
|
CLASS="QUOTE"
|
|
>"self-powered"</SPAN
|
|
>, 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.</P
|
|
><P
|
|
>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.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="modems"
|
|
></A
|
|
>3.10. Modems</H2
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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).</P
|
|
><DIV
|
|
CLASS="note"
|
|
><P
|
|
></P
|
|
><TABLE
|
|
CLASS="note"
|
|
WIDTH="100%"
|
|
BORDER="0"
|
|
><TR
|
|
><TD
|
|
WIDTH="25"
|
|
ALIGN="CENTER"
|
|
VALIGN="TOP"
|
|
><IMG
|
|
SRC="../images/note.gif"
|
|
HSPACE="5"
|
|
ALT="Note"></TD
|
|
><TD
|
|
ALIGN="LEFT"
|
|
VALIGN="TOP"
|
|
><P
|
|
>If you live somewhere with <EM
|
|
>really</EM
|
|
> 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
|
|
<A
|
|
HREF="http://www.usrobotics.com"
|
|
TARGET="_top"
|
|
>U.S. Robotics</A
|
|
> web site for
|
|
current product numbers and more detailed specifications.</P
|
|
></TD
|
|
></TR
|
|
></TABLE
|
|
></DIV
|
|
><P
|
|
>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).</P
|
|
><P
|
|
>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.</P
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="modem_format"
|
|
></A
|
|
>3.10.1. Internal vs. External</H3
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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
|
|
<SPAN
|
|
CLASS="QUOTE"
|
|
>"screaming-tty"</SPAN
|
|
> 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.</P
|
|
><P
|
|
>See <A
|
|
HREF="http://linuxmafia.com/~rick/faq/"
|
|
TARGET="_top"
|
|
>Rick's
|
|
Rants</A
|
|
> for extended discussion of this point.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="modem_pitfalls"
|
|
></A
|
|
>3.10.2. Pitfalls to Avoid</H3
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>If the abbreviation <SPAN
|
|
CLASS="QUOTE"
|
|
>"RPI"</SPAN
|
|
> occurs anywhere on the box,
|
|
don't even consider buying the modem. RPI (Rockwell Protocol Interface) is
|
|
a proprietary <SPAN
|
|
CLASS="QUOTE"
|
|
>"standard"</SPAN
|
|
> 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.</P
|
|
><P
|
|
>Also avoid anything called a <SPAN
|
|
CLASS="QUOTE"
|
|
>"Windows Modem"</SPAN
|
|
> or
|
|
<SPAN
|
|
CLASS="QUOTE"
|
|
>"WinModem"</SPAN
|
|
>, <SPAN
|
|
CLASS="QUOTE"
|
|
>"HCF"</SPAN
|
|
>, or <SPAN
|
|
CLASS="QUOTE"
|
|
>"HSP"</SPAN
|
|
>; 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). </P
|
|
><P
|
|
>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".</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect3"
|
|
><H3
|
|
CLASS="sect3"
|
|
><A
|
|
NAME="AEN317"
|
|
></A
|
|
>3.10.3. Fax Modems</H3
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>Avoid <SPAN
|
|
CLASS="QUOTE"
|
|
>"Class 1"</SPAN
|
|
> and <SPAN
|
|
CLASS="QUOTE"
|
|
>"Class 2"</SPAN
|
|
> modems. Look
|
|
for <SPAN
|
|
CLASS="QUOTE"
|
|
>"Class 2.0"</SPAN
|
|
> for the full EIA-standard command set.</P
|
|
><P
|
|
>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:</P
|
|
><P
|
|
></P
|
|
><DIV
|
|
CLASS="variablelist"
|
|
><DL
|
|
><DT
|
|
>V.29</DT
|
|
><DD
|
|
><P
|
|
> CCITT standard for Group III fax encoding at 9600bps</P
|
|
></DD
|
|
><DT
|
|
>V.17</DT
|
|
><DD
|
|
><P
|
|
> CCITT standard for Group III fax encoding at
|
|
14400bps</P
|
|
></DD
|
|
></DL
|
|
></DIV
|
|
><P
|
|
>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:</P
|
|
><P
|
|
><I
|
|
CLASS="firstterm"
|
|
>Class 1</I
|
|
> — base EIA standard for fax
|
|
control as extensions to the Hayes AT command set.</P
|
|
><P
|
|
><I
|
|
CLASS="firstterm"
|
|
>Class 2.0</I
|
|
> — enhanced EIA standard
|
|
including compression, error correction, station ID and other
|
|
features.</P
|
|
><P
|
|
><I
|
|
CLASS="firstterm"
|
|
>Class 2</I
|
|
> — marketroidian for anything
|
|
between Class 1 and Class 2.0. Different <SPAN
|
|
CLASS="QUOTE"
|
|
>"Class 2"</SPAN
|
|
> modems
|
|
implement different draft subsets of the 2.0 standard, so <SPAN
|
|
CLASS="QUOTE"
|
|
>"Class
|
|
2"</SPAN
|
|
> fax software won't necessarily drive any given <SPAN
|
|
CLASS="QUOTE"
|
|
>"Class
|
|
2"</SPAN
|
|
> modem.</P
|
|
><P
|
|
>There's also a proprietary Intel "standard" called CAS, Communicating
|
|
Applications Specification. Ignore it; only Intel products support it.</P
|
|
></DIV
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="printers"
|
|
></A
|
|
>3.11. Printers</H2
|
|
><P
|
|
>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!</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>(There used to be a problem with <SPAN
|
|
CLASS="QUOTE"
|
|
>"GDI printers"</SPAN
|
|
> and
|
|
<SPAN
|
|
CLASS="QUOTE"
|
|
>"WinPrinters"</SPAN
|
|
> 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.)</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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 <EM
|
|
>lot</EM
|
|
> of pixels on it. At
|
|
today's prices, paying the small premium for Postscript capability makes
|
|
sense.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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...)</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="power_protection"
|
|
></A
|
|
>3.12. Power Protection</H2
|
|
><P
|
|
>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 <A
|
|
HREF="http://www.tldp.org/HOWTO/UPS-HOWTO"
|
|
TARGET="_top"
|
|
>UPS
|
|
HOWTO</A
|
|
> that provides more complete coverage of what used to be in
|
|
this section.</P
|
|
></DIV
|
|
><DIV
|
|
CLASS="sect2"
|
|
><H2
|
|
CLASS="sect2"
|
|
><A
|
|
NAME="rfi"
|
|
></A
|
|
>3.13. Radio Frequency Interference</H2
|
|
><P
|
|
>(Thanks to Robert Corbett <Robert.Corbett@Eng.Sun.COM> for
|
|
contributing much of this section)</P
|
|
><P
|
|
>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).</P
|
|
><P
|
|
>FCC regulations recognize two classes of computer:</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
><P
|
|
>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.</P
|
|
></DIV
|
|
></DIV
|
|
><DIV
|
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><TD
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HREF="overview.html"
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