3. Buying the BasicsIn this section, we cover things to look out for that are more or less
independent of price-performance tradeoffs, part of your minimum system
for running Unix. Issues like your choice of disk, processor, and bus (where there is
a strong tradeoff between price and capability) are covered in the section
on What To Optimize. 3.1. How To Pick Your ProcessorRight now (early 2004), the chips to consider for running Unix are
the Pentium IVs and their clone equivalents from AMD or Cyrix — or,
if your budget will stand it, the AMD Opteron. The Pentium IV is something
of a dog (very poor price-performance, actually slower than a III on some
benchmarks), and the Itanium isn't out of the starting gate. 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
system offered. In the last few years I've become a big fan of
the AMD Athlon line — faster, cheaper, and better-designed than
Intel Pentiums. 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 ftp://ftp.cdf.toronto.edu/pub/spectable.
That document recommends (and I do too) that you read the SPEC FAQ at
http://www.specbench.org/spec/specfaq.html
to get background before browsing the table. 3.2. Bus WarsThe 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 are effectively just two
—PCI-X for desktop/tower machines and PCMCIA for laptops; even PCI is
now legacy technology. I used to recommend dual-bus PCI/ISA boards, but no longer do. The
on-board USB support and PS/2 mouse port now common on motherboards made
the difference, it means you no longer need ISA even internally (and PCI
cards are cheap these days). For your new desktop machine, go PCI-X
only. In the laptop market everything is PCMCIA. PCMCIA peripherals are
about the size of credit cards (85x54mm) and vary in thickness between
5 and 10mm. They have the interesting feature that they can be
hot-swapped (unplugged out and plugged in) while the computer is on.
However, they are seldom seen in desktop machines. They require a
special daemon to handle swapping, which is now standard under
Linux. 3.3. One Disk or Two?I always build with two disks — one "system" disk
and one "home" disk. There are two good reasons to do this
that have nothing to do with the extra capacity. One of them is the
performance advantage of being able to interleave commands to different
physical spindles that we discussed above. The other is that I am quite a
bit less likely to lose two disks at once than I am to trash a single
one. Let's suppose you have a fatal disk crash. If you have only one
disk, goodbye Charlie. If you have two, maybe the crashed one was your
system disk, in which case you can buy another and mess around with a new
Linux installation knowing your personal files are safe. Or maybe it was
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 did keep backups, right?). Your performance-tuning choice is IDE versus SCSI. We'll have more
to say about that in Section 4. 3.4. Getting Down to CasesI used to say that cases are just bent metal, and that it doesn't
much matter who makes those. Unfortunately, this isn't true any more.
Processors run so hot these days that fans and airflow are a serious
concern. They need to be well designed for proper airflow
throughout. Look for the following quality features: Aluminum rather than steel. It's lighter and conducts
heat better. Unobstructed air intake with at least one fan each
(in addition to the power supply and processor fans) No sharp metal edges. You doon't want to shred
your hands when you're tinkering with things. There shouldn't be any hot spots (poor air flow). Sturdy card clips. Some poorly-designed cases allow cards
to wiggle out of their slots under normal vibration. Effective and easy to use mechanisms for attaching hard
drives, CD-ROM, CD-R/W, DVDs, etc.
If you're fussy about RFI (Radio-Frequency Interference), it's worth
finding out whether the plastic parts of the case have conductive coating
on the inside; that will cut down emissions significantly, but a few cheap
cases omit it. Should you buy a desktop or tower case? Our advice is go with tower
unless you're building a no-expansions personal system and expect to be
using the floppies a lot. Many vendors charge nothing extra for a tower
case, and the cost difference will be trivial even if they do. What you
get for that is less desktop clutter, more and bigger bays for expansion,
and often (perhaps most importantly) a beefed-up power-supply and fan.
Putting the box and its fan under a table is good for maybe 5db off the
effective noise level, too. Airflow is also an issue; if the peripheral
bays are less cramped, you get better cooling. Be prepared to buy
extension cables for your keyboard and monitor, though; vendors almost
never include enough flex. The airflow thing is a good argument for a full- or mid-tower rather
than the ‘baby tower’ cases some vendors offer. However, smaller
towers are getting more attractive as boards and devices shrink and
more functions migrate onto the motherboard. A state of the art
system, with all 3" disks, 300W power supply, half-size motherboard,
on-board IDE and 64meg of RAM sockets, and half-sized expansion cards,
will fit into a baby or midsized tower with ample room for expansion;
and the whole thing will fit under a desk and make less noise than a
classic tower. For users with really heavy expansibility requirements,
rackmount PC cases do exist (ask prospective vendors). Typically a
rackmount case will have pretty much the same functionality as an
ordinary PC case. But, you can then buy drive racks (complete with
power supply), etc. to expand into. Also, you can buy passive
backplanes with up to 20 or so slots. You can either put a CPU card in
one of the slots, or connect it to an ordinary motherboard through one
of the slots. 3.5. Power Supplies and FansA lot of people treat power supplies as a commodity, so many
interchangeable silver bricks. We know better — cheap power supplies
go bad, and when they go bad they have a nasty habit of taking out the
delicate electronics they're feeding. Also, the power supply tends to be
the noisiest component in your system. Give preference to supplies with a Underwriter's Laboratories rating.
There's some controversy over optimum wattage level. On the one hand, you
want enough wattage for expansion. On the other, big supplies are noisier,
and if you draw too little current for the rating the delivered voltage can
become unstable. And the expected wattage load from peripherals is
dropping steadily. On the other hand, processors and their cooling fans
eat a lot more power than they used to. The choice is generally between 200W and 300W. After some years of
deprecating 300W-and-up supplies as overkill, I'm now persuaded it's time
to go back to them; a modern processor can consume 50-75W by itself, and
for the newer dual-processor board the power supply needs to be rated 450W
or up. About that annoying fan noise, ask if the power-supply fan on a
target system has a variable speed motor with thermostatic control;
this will cut down on noise tremendously. However, be aware that a
thermostatic sensor basically measures the temperature at
the sensor (typically within the power supply box) and
makes sure there is enough airflow to keep the power supply from
overheating. The sensor does not know a thing about the temperature
in certain hot spots likely to develop in a PC case (CPU, between
SIMMs, between drives mounted in vertically adjacent bays). This can be a problem, because in garden variety tower cases
there often isn't enough airflow to cool all components effectively
even if a single fan is going at full speed. This is especially true
if your computer has lots of add-on cards or hard disks (not much
airflow between cards or between drives). Note that the fan in the
power supply was basically designed to cool the power supply, not the
components in the case. Not providing additional fans is a sign of
cheapness. On tower PCs with "expensive" engineering (e.g. HP Vectra,
Compaq) one will find one to two extra fans besides the one in the
power supply. So the bottom line is, use thermostatic controls if you can to cut
noise. But if you want high reliability, use two or more fans. Modern
designs normally also have a small auxilliary fan mounted right over the
chip. 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 causes 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
Papst.
3.6. MotherboardsProvided you exercise a little prudence and stay out of the price
basement, motherboards and BIOS chips don't vary much in quality. There
are only six or so major brands of motherboard inside all those cases and
they're pretty much interchangeable; brand premiums are low to nonexistent
and cost is strictly tied to maximum speed and bus type. There are only
four major brands of BIOS chip (AMI, Phoenix, Mylex, Award) and not much to
choose between 'em but the look of the self-test screens (even the
"name" vendors use lightly customized versions of these). One
advantage Unix buyers have is that Unixes are built not to rely on the BIOS
code (because it can't be used in protected mode without more pain than
than it's worth). If your BIOS will boot properly, you're usually going to
be OK. Some good features to look for in a motherboard include: Gold-plated contacts in the expansion slots and RAM
sockets. Base-metal contacts tend to grow an oxidation layer which
can cause intermittent connection faults that look like bad RAM chips
or boards. (This is why, if your hardware starts flaking out, one of
the first things to do is jiggle or remove the boards and reseat them,
and press down on the RAM chips to reseat them as well —this may
break up the oxidation layer. If this doesn't work, rubbing what
contacts you can reach with a soft eraser is a good fast way to remove
the oxidation film. Beware, some hard erasers, including many pencil
erasers, can strip off the plating, too!) The board should be speed-rated as high as your
processor, of course. It's good if it's rated higher, so upgrade to a
faster processor is just a matter of dropping in the chip and a new
crystal. Voltage, temperature and fan speed monitoring hardware.
This is now common on motherboards based on recent iterations of the
Intel support chips, especially those designed for server use.
Linux supports drivers that can read this hardware, and monitoring
can help you spot incipient board failures.
If you're changing a motherboard, see the
Installing a Motherboard page first. This one even has a Linux
note. The dominant form factor now is still ATX, but there is a complete
redesign called BTX coming down the pike very shortly (as in, later in
2004). 3.7. MemoryAll current PC designs include a cacheing memory controller and some
fast on-chip cache that combine to produce higher effective speeds.
Judging the cache design used to be one of the trickiest parts of
evaluating a motherboard, but that stuff is all baked into the processor
itself now. Leading-edge designs like the AMD Opteron even implement the
memory controller inside the processor itself, removing another source of
latency and design variations. For current motherboards with 133MHz Memory Bus support, PC133 should
be used instead of PC100; it gives 33% greater memory bandwidth at very
little additional cost. DDR-SDRAM and RDRAM are faster memory types that
retrieve data in chunks and give you faster throughput. So-called `PC266'
memory is designed for motherboards that transfer at 133 but double the
width of the front-side bus connecting processor and memory. As the throughput of processor-to-memory buses rises, memory latency
(bus cycles required for the first fetch in a chunk) is becoming a more
important statistic. Lower numbers are better. For more technical stuff on memory architectures, see The Ultimate Memory
Guide maintained by Kingston Technologies. 3.8. Monitor and VideoThe more pixels you can afford to put on screen, the better. There
are factors other than resolution and price that have a strong liveability
impact, however. A major one is the sheer amount of space big monitors
take up. It's not a dream system if the display tube won't fit on your
desk! Today's CRT monitors and LCD flatscrees both top out at
2048x1536 resolution (with a few special and extremely expensive
exceptions). As LCDs fall in price they are very close to parity
with CRTs, and look like an increasingly good choice. Their only
serious drawback for most uses is slow response time — twitch
games and video have a tendency to blur just a bit. Next, buy your card. The major issue here is matching the
card to the capacity of your monitor — you don't want to buy a card
and find it can't drive your monitor at its maximum capability. If
(unlike us) you're economizing, you also don't want to pay for more
card than your monitor can use. So once you've specified your monitor, find a video card with a
maximum video bandwidth equal to or just slightly higher than the
monitor's. That's how you know your video system is properly
balanced, with a minimum of wasted capacity. 3.8.1. Selecting a MonitorI used to carry a lot of material on different video standards,
interlacing, and flicker. That stuff is all obsolete now. Nobody makes
anything less capable than SVGA 1024x768 at 72 refreshes per second any
more, and all new monitors auto-negotiate with your video card to settle on
the resolutions they can support. An abbrebiation you may see is
"UXGA"; that means 1600x1200. The only situation in which you might have to do manual tuning is
when the monitor's resolution is higher than any of the standard mode line
X knows how to support. In February 2004 that's above 1920x1440. If you
find youself in this situation, see XFree86
Video Timings HOWTO . 3.8.1.1. What To Look For On The Spec Sheet.Dot pitch of 0.28 or smaller on a 12"-15" monitor;
0.30 is acceptable on larger ones, especially 19" to 21" screens (but
look extra hard at 0.25 21-inchers like the Viewsonic 21PS or Nokia
445X). 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. 72Hz or better vertical scan frequency, to cut
flicker. Does it have a tilt-and-swivel base? Adequate
controls, including both horizontal and vertical size and horizontal
and vertical centering? A linearity control, a trapezoidal control,
and a color-temperature control are all pluses; the last is
particularly important if you compose graphics on screen for hardcopy
from a printer.
If you can, buy your monitor from someplace that will let you
see the same monitor (the very unit you will walk out the door with,
not a different or `demo' unit of the same model) that will be on your
system. There's a lot of quality variation (even in "premium" monitor
brands) even among monitors of the same make and model. Another good reason to see before you buy, and carry it home
yourself, is that a lot of monitors are vulnerable to bumps. The yoke
can get twisted, producing a disconcerting tilt in the screen
image. The Caveat
Emptor guide has a good section on evaluating monitor
specifications. And there's a database of monitor specs at
The Big Old Monitor List. 3.8.1.2. Eric Buys A Big Monitor: Smart Shopping TipsIn early 1996 the good folks at O'Reilly Associates dropped
several $1000 checks on me in relatively quick succession (payment for
fast-turnaround technical reviews). I decided to use the money to
treat myself to a really good monitor. This page tells you how I did it. Specific specs and pricing
information will date quickly, but the method should still be good
years from now. My existing monitor wasn't bad —a 17-inch Swan 617 that I
could drive at a bit above 1024x768. Still, I yearned for more real
estate —especially vertical real estate, so I could view full
PostScript pages using a legible font. This brings us to our first prescription: be clear
about what you want. It's easy, and very expensive, to buy
more monitor than you'll really use. I knew I wanted something in the 19-to-21-inch range, with
1280x1024 or higher resolution. I knew this would probably cost me
about $2000, and could afford it. I knew I
didn't need one of the monster projection
monitors further upmarket, with screen sizes 24" and up. These
will typically cost you $4K or so and are too big for desktop use
anyway. I also knew I didn't need one of the special true-color monitors
designed for photo composition, making print separations, and so
forth. These creatures (always Trinitrons) have better, denser color
than conventional tubes but at a hefty price premium (and usually at
some cost in available resolution). If all you're going to do most of
the time is 16 or 256-color X screens, you don't need this
capability. Once you've settled on what you need, gather comparative
data. It was 1996, so I started out by making
phone calls to manufacturer 800 numbers. Then I discovered that
almost all the manufacturers had Web sites, with technical specs for
their monitors on them. Today, you'd go to the Web first. (This space used to include detailed technical data on what I
found " model numbers, resolutions, reviews of manufacturer
websites, etc." but I've removed it because it's all five years
out of data now.) This wasn't at all a hard call. The ViewSonic 21PS and Nokia
445X stood out from the pack immediately; their combination of high
bandwidth with a 21-inch screen size and ultra-fine .25 dot pitch
promised better performance than the general run of .28-pitch
monitors. Nor was the choice between the two very hard. ViewSonic's 21PS
is $600 less expensive than Nokia's 445X for very similar performance.
And, other things being equal, I'd rather buy a monitor from a
specialist monitor manufacturer than a general consumer electronics
outfit best known for its cellular phones. So I determined to order a ViewSonic 21PS. This left me with a second problem. My ATI Mach 32 can't drive
a monitor at higher than 1280x1024 resolution and 94MHz bandwidth. So
it wouldn't be able to drive the 21PS at 1600x1200. I wound up buying
a Mach 64. The combination worked wonderfully (two years later I discovered
that VA Linux Systems bought the
same monitor for its high-end systems). The only problem I have with
it is that monitor is way bright even dialed down
to its dimmest setting. You'll need a strong light in the room where
you install it. Also, be aware that the only really convenient way to
move one of these monster monitors is with a forklift! Eight years later, in 2004, all these shopping tips are good
—and the high-end Viewsonics are actually still among the best
monitors around. 3.8.2. Buying a Video CardVideo controllers translate byte values deposited in their video
memory by your GUI (usually an X server under Linux) into an analog RGB
signal which drives your monitor. The simplest kinds treat their video
memory as one big frame buffer, requiring the CPU to do all dot-painting.
More sophisticated "accelerated" cards offer operations such
as BitBlt so your X server can hack the video memory algorithmically.
These days almost all cards even at the low end actually have some
acceleration features. Cards are rated by the maximum number of analog signal changes they
can produce per second (video bandwidth). Video bandwidth can be used
to buy varying combinations of screen resolution and refresh speed,
depending on your monitor's capabilities. Another important variable of video cards is the size of their
on-board video RAM. Increased memory lets you run more colors at higher
resolutions. 4MB of video memory, which can drive 24-bit or
"true" color (16 million colors) at 1024x768, is pretty much
the minimum nowadays; most cards have more. The card's video RAM size has no effect on its speed. What does
affect speed is the type of memory on board.
VRAM (Video Random Access Memory) is fast but more expensive; it
features a dual-ported design allowing two devices (the CRT controller
and the CPU) to access the memory at the same time. DRAM (Dynamic
Random Access Memory) is is similar to the RAM used in main memories.
It is cheaper, more common, and slower (because the CRT controller and
the CPU must take turns accessing the video buffer). Effectively all cards made today use AGP, a special high-speed
attachment slot, and even low-end motherboards support it. That's
if your video isn't integrated right onto the motherboard, an
increasing trend. 3.9. Keyboards and MiceKeyboards are mostly generic nowadays. One useful piece of advice is
to not buy any desktop with "Internet" buttons on it; this is a sure sign
of a PC that's an overpriced glitzy toy. The coming thing is USB keyboards;
by the end of 2004 new machines probably won't have traditional keyboard
ports any more. Modern open-source Unixes handle these just fine. Mice and trackballs used to be simple; then, thanks to Microsoft,
they got complicated. Now they're simple again; all ATX motherboards have
a mouse port, and all new mice are made to plug into it. They're going to
get simpler; dedicated mouse ports are on the way out, and USB mice will
soon dominate. XFree86 autodetects your mouse when it starts up, so
configuration is not a big deal any more. Beware that most clone vendors, being DOS 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. Your humble editor really, really likes the Logitech TrackMarble, an
optical trackball that eliminates the chronic roller-fouling problems of
the older TrackMan. They're well-supported by XFree86 (type MouseMan), so
any Linux or BSD will accept them. 3.10. Floppy DrivesThere's not 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 ‘hard-shell’ floppies with 1.44MB capacity
anymore. You'll probably never use floppies for anything but first boot of a
new operating system. Bootable CD-ROMs, standard of most PCs these days,
eliminate even that use. So go ahead and settle for cheap Mitsumi and Teac
floppy drives. There are no ‘premium’ floppy drives anymore.
Nobody bothers. It's possible your system won't even include one. No loss in 2004. 3.11. CD-ROM DrivesYou'll need a CD-ROM or DVD-ROM drive (you'll almost certainly be
installing your Linux from it!). You have a SCSI system, so get a SCSI
CD-ROM. That's pretty much the end of spec, as there are only a few models
of SCSI DVD-ROM and SCSI CD-ROMs are a very generic item. The only
significant price driver is their speed — 8x, 10x, or up (it's hard to
find lower speeds anymore). Note that however high a read speed the
brochure cites, these drives basically don't get any faster in practice
above 12x. Big numbers like 40x are theoretical — what you'd get on an
uninterrupted sequential read of a perfectly balanced, perfectly clean
disk. Standard CD-ROMs hold about 650 megabytes of read-only data in a
format called ISO-9660 (formerly "High Sierra"). All current
Unixes now support these devices. In fact, most Unix and Linux software is
now distributed on ISO-9660 CD-ROM, a cheaper and better method than the
QIC tapes we used to use. Modern CD-ROM drives may be driven through either SCSI or enhanced
IDE (ATAPI). Some used to come with dedidcated interface cards, but those
are obsolete. A few external CD-ROMs come with a parallel-port interface.
Avoid these; they tend to have very slow transfer rates. Any CD-ROM you buy should be at least a "double-spin"
drive meeting the MPC2 (Multimedia PC) standard of a 300K/sec transfer rate
when reading. digital data. The older single-speed drives, which only
supported the 150K/sec rate Red Book standard for audio CDs, are obsolete.
The lowest speed you can buy these days is 4X (600K/sec). 6X, 8X, 10X,
12X, 24X, 32X, 40X, and 56X are available. Note that however high a read
speed the brochure cites, these drives basically don't get any faster in
practice above 12x. Big numbers like 40x are theoretical —what you'd
get on an uninterrupted sequential read of a perfectly balanced, perfectly
clean disk. CD-ROM access times about 280ms for high-end double-speed drives (to
put this in perspective, it's about 30 times slower than a typical 9ms hard
disk, but considerably faster than a tape). Accordingly, modern 32X
drives are about half the speed of a hard drive. Most CD-ROMS will include a headphone jack so you can play audio
CDs on them. Better-quality 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. CD-ROM formats are still an area of some confusion. A slight
enhancement of the original "High Sierra" CD-ROM filesystem format
(designed for use with DOS, and limited to DOS's 8+3 file-naming
convention) has been standardized as ISO-9660. There is a de-facto Unix standard called ‘Rock Ridge’
pioneered by the Sun User's Group shareware CD-ROMs. This is a way of
putting an extra layer of indirection on an ISO-9660 layout that preserves
Unix's long dual-case filenames. Some Unixes (notably Linux, netBSD,
freeBSD and BSD/OS) can mount Rock Ridge filesystems. More much more detail on CD-ROMs, CD-ROM standards and how to
buy drives is available in the alt.cdrom FAQ, available for FTP as cdrom.com:/cdrom/faq. It is also
archived in the news.answers tree at rtfm. This FAQ includes
comparison tables of numerous drive types, CD-ROM sources, and
ordering information. 3.12. DVD Drives(Most of this section courtesy of James Turinsky.) Most drives manufactured after January 1st 2000, and some drives prior
to that have come installed with something called RPC2. When a drive is RPC2, it means that it stores the Region code physically
within the drive. This means that nothing you do on the software level
will be of any help (including using DVD Genie or formatting your hard
drive). The only means of bypassing this Regional Protection Scheme is by
using a firmware patch. A firmware patch is a special piece of software
written for a specific DVD Drive model. It will only works on that specific
model. The original role of the firmware patch was to fix minor flaws in the
drive logic (a piece of programmable software within the drive, also
referred to as a "Firmware"). This logic also controls the Region
Checks, so some inventive programmers have modified these firmware
patches to remove the portion of logic that does the Regional checks,
thus making the drive region-free (RPC1 stands for region free). However, since a firmware patch is specific to one drive model, it's
impossible to make a global fix for all drives on the hardware level.
This limitation requires programmers to modify each firmware patch that
comes out for various drives. And here lies the problem. Modifying a
firmware is not a simple task, it requires good understanding of the
hardware and some advanced programming skills. To top this off, there
are quite a few DVD Drive models out there, and not as many programmers
with the skill that can access these drives. So in reality, not all
drives have firmware patches that can make the drive region free. So some foresight is required when buying a new DVD Drive. You should
check if someone already released a patched firmware for the model you
wish to buy. For more, see the Firmware
Patches site. 3.13. Sound Cards and SpeakersLook for the following features as a minimum in your sound card: 16-bit sampling (for 65536 dynamic levels rather
than 256). Mono and stereo support. Full-duplex mode. Sampling rates ranging fron 8K/sec (voice-quality)
through 11KHz (AM-radio quality), 22KHz (FM-radio quality) and
standard audio (44.1KHz). MIDI interface via a standard 15-pin D-shell
connector. RCA output jacks for headphones or speakers. A microphone jack for sound input.
Older and cheaper cards use FM synthesis. This synthesis uses a
combination of sine waves to imitate the sounds of the different
instruments. The result is like the sound tracks of most computer
games sold a few years ago; imitation music with an arcade-like
sound. The method used by most modern sound boards is called wave table
synthesis. In this method, digitized samples of actual instrument
sounds are used as templates for the tones generated by the MIDI
commands. Wave table cards vary in the quantity and quality of
samples; one figure of merit often quoted is the wave table ROM size
(often 4MB or 8MB). Also some boards have wavetable RAM that can
store samples loaded from a disk. Soundcards with DSP (Digital Signal Processing) can perform synthesis
effects on board, relieving the CPU for other tasks. Some DSP chips
are even software-programmable. Some high-end cards even include 3D
sound effects. Whether the system used is SRS (Sound Retrieval
System), Q-Sound, or Spatializer, it is designed to improve the
perceived stereo effect of your speakers. These 3D effects work by
delaying the timing of certain portions of the audio signal so that
different frequencies hit your ear at slightly different times. The
downside is that some of the cards equipped with 3D sound add a
noticeable amount of noise to the card's output. If you play a lot of computer games, you'll need to pay attention to
compatibility. DOS games are written almost exclusively for the
Creative Labs specification; you will need a card that is 100% Sound
Blaster compatible. Many vendors do not license the Creative Labs
specification but claim that their cards are 100% game
compatible. This means that the sound will work, but not all sounds
that you hear will be the ones that the game programmers intended. If
you play many DOS games, it would be best to buy a Sound Blaster and
save yourself a migraine. Lastly, try to avoid sound cards with built-in amplifiers that are
more powerful than 4 watts/channel. Sound cards that have more
powerful amplifiers are said to have the problem of adding noise to the
card's output. Use powered speakers with a 4 watt/channel card to
solve this problem. Most cards are equipped with 4 watts/channel
anyway. Wavetable cards are so inexpensive these days that it's almost
worth their additional cost over a regular FM synthesis card. If you
decide to settle for an FM card, make sure that there is a
daughterboard made for the card that will let you upgrade to wavetable
synthesis. In some cases, however, the wavetable card is cheaper than
buying an FM card and then deciding that you want the wavetable
upgrade. If you do decide on the wavetable as your card of choice, PC
Magazine rated the best MIDI wavetables (MIDI being the most important
feature in my opinion) the Media Vision Premium 3-D, Media Vision Pro
3-D, Creative Labs Sound Blaster AWE32, and the Turtle Beach Monterey
(although there are value editions of the Sound Blaster 32 that have
fewer ROM instrument samples but maintain the superior MIDI wavetable
synthesis). In speakers, look for a magnetically-shielded enclosure with volume,
bass and treble controls. Some speakers run off the card's 4-watt
signal; others are "self-powered", using batteries or a separate
power supply. Your major buying choice is which one of these options
to pursue. 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 "Doom" with sound even if your sound board won't
accept the audio cable connector. 3.14. Backup devicesIt's good to be able to make backups that you can separate from your
system and store off-site in case of disaster. Two years ago, 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. 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. 3.15. ModemsThis section will give you a thumbnail sketch of the modem types
available out there, one tuned for the typical Unix installation's
needs. 3.15.1. The Simple AnswerThe modem market has stabilized, with a clear leader at a reasonable
price. Demand for modems is dropping as more and more people get broadband
Internet through DSL and cable. If you need a modem and can spend $94, get
a U.S. Robotics V.92 external. You can then know that you've got the best
and skip the rest of this section. 3.15.2. Overview of the Modem MarketThe modem market is like consumer electronics (and unlike the
computer market as a whole) in that price is a very poor predictor of
performance. For ordinary file transfers, some $50 modems are better than
some $150 modems. Paying top dollar mainly buys you better tolerance of
poor connections and better performance at heavy-duty bi-directional
transfers (such as you would generate, for exmaple, using SLIP or PPP over
a leased line to an Internet provider). In today's market, the typical modem does a nominal 56kbps
—V.90 and V.92 plus V.29 or V.17 fax transmission and reception (over
plain old phone lines you won't get more than 53K of that). You don't see
much in the way of slow/cheap to fast/expensive product ranges within a
single brand, because competition is fierce and for many modem board
designs (those featuring DSP (Digital Signal Processor) chips run by a
program in ROM) adding a new protocol is basically a software
change. 3.15.3. Internal vs. ExternalMost 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. Pay that premium — being able to see the blinkenlights on
the external ones will help you understand and recover from
pathological situations. For example, if your Unix system is prone to
"screaming-tty" syndrome, you'll quickly learn to recognize the
pattern of flickers that goes with it. Punch the hangup/reset button
on an external modem and you're done — whereas with an internal
modem, you have to go root and flounder around killing processes and
maybe cold-boot the machine just to reset the card. See Rick's
Rants for extended discussion of this point. 3.15.4. Pitfalls to AvoidIf the abbreviation "RPI" occurs anywhere on the box,
don't even consider buying the modem. RPI (Rockwell Protocol Interface) is
a proprietary "standard" that allows modem makers to save a
few bucks at your expense by using a cheap-jack Rockwell chipset that
doesn't do error correction. Instead, it hands the job off to a modem
driver which (on a Unix machine) you will not have. Also avoid anything called a "Windows Modem" or
"WinModem", "HCF", or "HSP"; these
lobotomized pieces of crap require a Windows DLL to run. They will eat up
to 25% of your processor clocks during transfers, and hog high-priority
interrupts (causing your machine to stall under Windows even if your
processor still has spare cycles). Multi-user Unix eats enough processor clocks that you want to be
sure of good hardware buffering in your UART — that is, enough
of it to avoid losing characters between modem and PC if the OS is a
bit slow responding to an interrupt (V.42bis in hardware won't detect
this!). This means you want a 16550A or equivalent UART. If you're
using an external modem, this is an issue about your serial-port
board(s). If you're using an internal modem, the UART is on the modem
card itself. So, when buying internal modems,
ask what the UART type is. If the vendor says
16540, lose them. Many fax modems come with bundled MS-DOS fax software that is at
best useless under Unix, and at worst a software kluge to cover
inadequate hardware. Avoid these bundles and buy a bare modem —
it's cheaper, and lowers the likelihood that something vital to your
communications needs has been left out of the hardware. Avoid "Class 1" and "Class 2" modems. Look
for "Class 2.0" for the full EIA-standard command set. 3.15.5. What to BuyWhat you want, these days, is a V.92 modem. V.92, formally,
is the ITU-T recommendation for asymmetric data signalling
rates of up to 56Kbps in the direction of a digitally connected server
to a capable client, and up to 33.6Kbps in the direction of the client
to the server. The technology is based on eliminating restrictions imposed by the
conversion of analog signals to digital form in the downstream data path
(server -> client). Data flow in the server to client direction does not
occur in the form of a modulated carrier, it is instead sent as binary
numbers representative of 256 possible voltage levels. The reason for the
asymmetrical send/receive rates is because in the direction from the client
to the server it is not possible to use a digital coding scheme and make it
work as well as V.34 does, thus V.34 is used instead. It isn't possible
because the telco's line card has a codec that is a much better digital
level changer for the transmit direction than it is for the receive
direction. The codec used in the customer's modem is, in that respect,
somewhat more sophisticated and was designed to work as a fairly good level
changer in the receive direction (which the telco's codec was not designed
to do). Note: Achievable bit rates are limited to less than 56kbps in
the United States by FCC regulations that limit power input to the
network. 3.15.6. Fax ModemsFax capability is included with most all modems these days; it's
cheap for manufacturers, being basically a pure software add-on. The
CCITT also sets fax protocol standards. Terms to know: - V.29
CCITT standard for Group III fax encoding at 9600bps - V.17
CCITT standard for Group III fax encoding at
14400bps
There's a separate series of standards for software control of fax
modems over the serial line maintained by the Electronics Industry
Association and friends. These are: Class 1 — base EIA standard for fax
control as extensions to the Hayes AT command set. Class 2.0 — enhanced EIA standard
including compression, error correction, station ID and other
features. Class 2 — marketroidian for anything
between Class 1 and Class 2.0. Different "Class 2" modems
implement different draft subsets of the 2.0 standard, so "Class
2" fax software won't necessarily drive any given "Class
2" modem. There's also a proprietary Intel "standard" called CAS, Communicating
Applications Specification. Ignore it; only Intel products support it. The GNU toolset includes an open-source fax transmission and
reception toolset, Netfax. Look for it at prep.ai.mit.edu:pub/gnu/fax-*.
It says it requires a modem conforming to the "Class 2"
control standard, but you'd be safest getting a 2.0-conformant modem for
reasons explained above. Netfax also requires GNU Ghostscript to do
Postscript handling for it. 3.16. PrintersThere really isn't all that much to be said about printers; the market is
thoroughly commoditized and printer capabilities pretty much independent
of the rest of your hardware. The PC-clone magazines will tell you what
you need to know about print quality, speed, features, etc. The business
users they feed on are obsessed with all these things. (There used to be a problem with "GDI printers" and
"WinPrinters" that only worked with Windows —they
required special drivers that took over your CPU to do image processing,
These were such a bad idea that they have basically disappeared off the
market.) Most popular printers are supported by GhostScript, and so it's easy
to make them do PostScript. If you're buying any letter-quality
printer (laser or ink-jet), check to see if it's on GhostScript's
supported device list —otherwise you'll have to pay a premium for
Postscript capability! Postscript is still high-end in the MS-DOS
market, but it's ubiquitous in the Unix world. Warning, however: if you're using ghostscript on a non-Postscript
printer, printspeed will be slow, especially with a serial printer. A
bitmapped 600 dpi page has a lot of pixels on it. At
today's prices, paying the small premium for Postscript capability makes
sense. If you're buying a printer for home, an inkjet is a good choice
because it doesn't use gobs of power and you won't have the
toner/ozone/noise/etc mess that you do with a laser. If all
you want is plain-ASCII, dot-matrix is cheaper to buy and run — if
you can find one. Inexpensive ink-jets and lasers have almost driven
them off the market. Inkjets are great in that they're cheap, many of them do color, and
there are many kinds which aren't PCL but are understood by
Ghostscript anyway. If you print very infrequently (less than weekly,
say), you should be careful to buy a printer whose print head gets
replaced with every ink cartrige: infrequent use can lead to the
drying of the ink, both in the ink cartrige and in the print head.
The print heads you don't replace with the cartrige tend to cost
nearly as much as the printer (~$200 for an Epson Stylus 800) once the
warranty runs out (the third such repair, just after the warranty
expired, totalled one informant's Stylus 800). Be careful, check
print head replacement costs ahead of time, and run at least a
cleaning cycle if you don't actually print anything in a given week.
(Conversely, toner starts out dry, and ribbon ink won't evaporate for
years...if you truly print only rarely, but neither a dot matrix nor a
laser makes sense, consider buying no printer and taking your
PostScript files to a copy shop...) A parallel interface is a cheap way to make your printer
print a lot faster than a serial line, and everyone's got a parallel port
in their PC. Nowadays, though, a lot of printers are moving to
Universal Serial Bus. Parallel ports may be obsolete soon. 3.17. Power ProtectionI strongly recommend that you buy a UPS to protect your hardware and
data. MOV-filtered power bars make nice fuses (they're cheap to replace),
but they're not enough. I have written a UPS
HOWTO that provides more complete coverage of what used to be in
this section. 3.18. Radio Frequency Interference(Thanks to Robert Corbett <Robert.Corbett@Eng.Sun.COM> for
contributing much of this section) Radio Frequency Interference (RFI) is a growing problem with PC-class
machines. Today's processor speeds are such that the electromagnetic noise
generated by a PC's circuitry in normal operation can degrade or jam radio
and TV reception in the neighborhood. Such noise is called Radio Frequency
Interference (RFI). Computers, as transmitting devices, are regulated by
the Federal Communications Commission (FCC). FCC regulations recognize two classes of computer: If a PC is to be used in a home or apartment, it must be
certified to be FCC class B. If it is not, neighbors have a legal
right to prevent its use. FCC class A equipment is allowed in
industrial environments. Many systems are not FCC class B. Some manufacturers build
boxes that are class B and then ship them with class A monitors or
external disk drives. Even the cables can be a source of RFI. It pays to be cautious. For example, the Mag MX17F is FCC class
B. There are less expensive versions of the MX17 that are not. The
Mag MX17 is a great monitor (I wish I had one). It would be painful
to own one and not be allowed to use it. An upgradeable system poses special problems. A system that is
FCC class B with a 33 MHz CPU might not be when the CPU is upgraded to
a 50 or 66 MHz CPU. Some upgrades require knockouts in the case to be
removed. If a knockout is larger than whatever replaces it, RFI can
leak out through the gap. Grounded metal shims can eliminate the
leaks. Even Class B systems don't mix well with wireless phonesets (not cellular
phones, but the kind with a base station and antennaed headset). You'll often
find a wireless phone hard to use withing 20 feet of a Class B machine. To cut down on RFI, get a good metal case with tight joints, or at
least make sure any plastic one you buy has a conductive lining. You
can also strip the painted metal-to-metal contacting parts of paint so
that there's good conductive metal contact. Paint's a poor conductor
in most cases, so you can get some benefit from this. |
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