3. Buying the Basics

In 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 Processor

Right 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 Wars

The system bus is what ties all the parts of your machine together. This is an area in which progress has simplified your choices a lot. There used to be no fewer than four competing bus standards out there (ISA, EISA, VESA/VLB, PCI, and PCMCIA). Now there 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 Cases

I used to say that cases are just bent metal, and that it doesn't much matter who makes those. Unfortunately, this isn't true any more. Processors run so hot these days that fans and airflow are a serious concern. They need to be well designed for proper airflow throughout.

Look for the following quality features:

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 Fans

A lot of people treat power supplies as a commodity, so many interchangeable silver bricks. We know better — cheap power supplies go bad, and when they go bad they have a nasty habit of taking out the delicate electronics they're feeding. Also, the power supply tends to be the noisiest component in your system.

Give preference to supplies with a Underwriter's Laboratories rating. There's some controversy over optimum wattage level. On the one hand, you want enough wattage for expansion. On the other, big supplies are noisier, and if you draw too little current for the rating the delivered voltage can become unstable. And the expected wattage load from peripherals is dropping steadily. On the other hand, processors and their cooling fans eat a lot more power than they used to.

The choice is generally between 200W and 300W. After some years of deprecating 300W-and-up supplies as overkill, I'm now persuaded it's time to go back to them; a modern processor can consume 50-75W by itself, and for the newer dual-processor board the power supply needs to be rated 450W or up.

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. Motherboards

Provided you exercise a little prudence and stay out of the price basement, motherboards and BIOS chips don't vary much in quality. There are only six or so major brands of motherboard inside all those cases and they're pretty much interchangeable; brand premiums are low to nonexistent and cost is strictly tied to maximum speed and bus type. There are only four major brands of BIOS chip (AMI, Phoenix, Mylex, Award) and not much to choose between 'em but the look of the self-test screens (even the "name" vendors use lightly customized versions of these). One advantage Unix buyers have is that Unixes are built not to rely on the BIOS code (because it can't be used in protected mode without more pain than than it's worth). If your BIOS will boot properly, you're usually going to be OK.

Some good features to look for in a motherboard include:

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. Memory

All 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 Video

The 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 Monitor

I 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 . 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. Eric Buys A Big Monitor: Smart Shopping Tips

In 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 Card

Video 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 Mice

Keyboards 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 Drives

There'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 Drives

You'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 Speakers

Look for the following features as a minimum in your sound card:

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 devices

It'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. Modems

This 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 Answer

The 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 Market

The modem market is like consumer electronics (and unlike the computer market as a whole) in that price is a very poor predictor of performance. For ordinary file transfers, some $50 modems are better than some $150 modems. Paying top dollar mainly buys you better tolerance of poor connections and better performance at heavy-duty bi-directional transfers (such as you would generate, for exmaple, using SLIP or PPP over a leased line to an Internet provider).

In today's market, 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. External

Most modems come in two packagings: internal, designed to fit in a PC card slot, and external, with its own case, power supply, and front-panel lights. Typically you'll pay $20 to $30 more for an external modem than you will for the internal equivalent. You'll also need a serial 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 Avoid

If the abbreviation "RPI" occurs anywhere on the box, don't even consider buying the modem. RPI (Rockwell Protocol Interface) is a proprietary "standard" that allows modem makers to save a few bucks at your expense by using a cheap-jack Rockwell chipset that doesn't do error correction. Instead, it hands the job off to a modem driver which (on a Unix machine) you will not have.

Also avoid anything called a "Windows Modem" or "WinModem", "HCF", or "HSP"; these lobotomized pieces of crap require a Windows DLL to run. They will eat up to 25% of your processor clocks during transfers, and hog high-priority interrupts (causing your machine to stall under Windows even if your processor still has spare cycles).

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 Buy

What 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 Modems

Fax 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:


CCITT standard for Group III fax encoding at 9600bps


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. Printers

There really isn't all that much to be said about printers; the market is thoroughly commoditized and printer capabilities pretty much independent of the rest of your hardware. The PC-clone magazines will tell you what you need to know about print quality, speed, features, etc. The business users they feed on are obsessed with all these things.

(There used to be a problem with "GDI printers" and "WinPrinters" that only worked with Windows —they required special drivers that took over your CPU to do image processing, These were such a bad idea that they have basically disappeared off the market.)

Most popular printers are supported by GhostScript, and so it's easy to make them do PostScript. If you're buying any letter-quality printer (laser or ink-jet), check to see if it's on GhostScript's supported device list —otherwise you'll have to pay a premium for Postscript capability! Postscript is still high-end in the 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 Protection

I strongly recommend that you buy a UPS to protect your hardware and data. MOV-filtered power bars make nice fuses (they're cheap to replace), but they're not enough. I have written a UPS HOWTO that provides more complete coverage of what used to be in this section.

3.18. 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.