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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 I/O bus (where there is a significant tradeoff between price and capability) are covered in the section on What To Optimize.
An effect of PC commoditization is that there aren lots of things you used to have to worry about that don't matter any more, because the market has completely flattened out. We list these here to get them out of the way.
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 on servers, and PCIe for desktop/tower machines. Even PCI is now legacy technology, and the PCMCIA bus that seemed so important a few years back has been reduced to near-irrelevance by Ethernet and WiFi hardware built onto motherboards. The newcomer is PCIe, which is (in late 2007) a ‘video-card-mostly’ bus, though it seems to be gaining in popularity for other uses too on mainstream desktop motherboards, whereas PCI-X is only found on higher end ‘server’ motherboards.
Judging the memory-controller and 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. This removed a large source of latency and design variations. It also killed off the plethora of different RAM types that used to be out there.
Today's advice is very simple. Make sure the memory is rated for your machine's bus speed, then buy as much as you can afford to stuff in your machine.
For more technical stuff on memory architectures, see The Ultimate Memory Guide maintained by Kingston Technologies.
Keyboards are mostly generic nowadays. One useful piece of advice is to not buy any desktop machine with "Internet" buttons on it; this is a sure sign of a PC that's an overpriced glitzy toy. Nowadays keyboards with a USB connector are the norm, rather than the older dedicated connectors; 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. Again, USB mice have replaced the older PS/2-style dedicated connector. XFree86 autodetects your mouse when it starts up, so configuration is not a big deal any more.
Some PC vendors, being Windows-oriented, still bundle two-button mice. Thus, you may have to buy your own three-button (or two button and a scroll wheel) mouse. Ignore the adspeak about dpi and pick a mouse or trackball that feels good to your hand.
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 X, so any Linux or BSD will accept them.
There's no longer much to be said about floppy drives. They're cheap, they're generic, and the rise of CD-ROM and DVD-ROM drives as a cheap distribution medium has made them much less important than formerly. You only ever see the 3.5-inch ‘hard-shell’ floppies with 1.44MB capacity anymore.
Bootable CD-ROMs killed off the last use of floppies, which was OS installation. So go ahead and settle for cheap Mitsumi and Teac floppy drives. There are no ‘premium’ floppy drives anymore. Nobody bothers.
It's possible your system won't even include one. No loss.
Standard CD-ROMs hold about 650 megabytes of read-only data in a format called ISO-9660 (formerly "High Sierra"). All current Unixes support these devices. 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.
CD-ROM speed used to be a big deal; vendors advertised 2X, 4X, all the way up to 52X. Vendors don't bother any more; the drives are all about equivalently fast now.
There are one or two minor features to watch for. 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.
Increasingly, DVD-ROM drives (and burners) are replacing CD-ROM drives as the default optical drive in PC systems. They have significantly larger capacity, and will read (and burn) CD media too. The cost difference now is so small that it is usually preferable to buy a DVD burner instead of a CD-ROM drive.
It's good to be able to make backups that you can separate from your system and store off-site in case of disaster. Until about 2001, tape drives still seemed like a good idea for personal systems, but I found I seldom used mine. Today, tape drive with high enough capacity to image today's huge hard disks are too expensive to make sense any more.
For the money you'd spend on a high-capacity tape drive (over $1000) it makes more sense to buy a laptop and a pile of CD-R or DVD-R or DVD+R media. Sit the laptop on your house Ethernet when you're not traveling, and back up the main machine to it every day, or oftener. Between the efficiency of rsync and the speed of 100-megabit Ethernet, this will be a lot faster than making a tape. Every once in a while, burn a set of backup CD-ROMs or DVDROMs.
But CD-ROMs aren't reusable; the cost piles up over time. An interesting alternative is a small external USB hard drive, especially if you can salvage an old laptop drive and put it in a USB enclosure. These enclosures are available for about $30; Google for "USB HD Enclosure". This is faster than a tape, cheaper and lighter than a full laptop. For faster transfer speeds, an enclosure that accepts eSATA connections as well as USB helps a lot (assuming your PC or notebook has an eSATA connector).
Right now (late 2007), the chips to consider for running Unix are the the 64-bit AMD Opteron or its Intel equivalents. We've basically passed the point at which 32-bit chips are interesting for new desktop systems; choosing one won't save you more than small change any more. The transition isn't complete in laptops yet, which are mostly still using 32-bit chips to minimize their power draw.
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 line. They used to be faster, cheaper, and better-designed than Intel processors; today Intel has clawed back the speed advantage, but AMD chips still deliver more performance than you're likely to be able to use and do it with lower power dissipation (thus, less noise and heat).
Many CPUs now are multi-core — that is, they have multiple CPUs on a single chip. This is very useful for doing something compute intensive (re-encoding video, compressing large archives, etc.) in the background and still having a responsive system for other work at the same time. At current prices, a dual-core CPU makes good sense for most desktop systems. If you are creating a server or have specialized computing needs you expect to be very CPU-intensive, quad-core is worth considering. Only at the very low end (sub US$50 CPUs) do single-core CPUs still make sense on desktop machines.
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.
Current CPUs are much faster than those of just a few years ago. As a result, unless your needs are highly specialized, spending more than about US$200 on a desktop CPU is hard to justify. Putting extra budget into more RAM or a faster disk subsystem will most likely result in greater benefit to most users.
I usually 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'll explain a bit later in the section on disks. 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?).
Given today's high capacity drives, another way to use two disks well is to set them up as a RAID1 (mirrored) array. This can be done in software or with a hardware RAID controller. This way if either of the two drives fail, the system will continue to function, no data is lost, and upon replacing the failed drive, the array can be rebuilt from the remaining working drive. Hard drives are consumable media, they do fail, so this approach (as well as good backups) is well worth considering.
Your performance-tuning choice is SATA versus SCSI (the older IDE and EIDE buses are now obsolete). We'll have more to say about that in Section 4.
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 SATA and 4GB of RAM sockets, and half-sized expansion cards, will fit into a baby or midsized tower with ample room for expansion; and the whole thing will fit under a desk and make less noise than a classic tower.
For users with really heavy 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.
A lot of people treat power supplies as a commodity, so many interchangeable silver bricks. We know better — cheap power supplies go bad, and when they go bad they have a nasty habit of taking out the delicate electronics they're feeding. Also, the power supply tends to be the noisiest component in your system.
Give preference to supplies with a Underwriter's Laboratories rating. There's some controversy over optimum wattage level. On the one hand, you want enough wattage for expansion. On the other, big supplies are noisier, and if you draw too little current for the rating the delivered voltage can become unstable. And the expected wattage load from peripherals is dropping steadily. On the other hand, processors and their cooling fans eat a lot more power than they used to.
The choice is generally between 200W and 300W. After some years of deprecating 300W-and-up supplies as overkill, I'm now persuaded it's time to go back to them; a modern processor can consume 50-75W by itself, and for the newer dual-processor board the power supply needs to be rated 450W or up.
Processors on modern motherboards run hot enough that all vendors have gone to embedded temperature sensors and variable-speed thermostat-controlled fans, out sheer self-defense (this used to be a high-end only feature).
To cut noise, look for 120mm fans rather than the old-style 80mm muffin fans. These can move the same amount of air per minute rotating at a lower tip speed, which means less vortex formation and less noise. These are now becoming standard even on cheap white-box hardware.
In garden-variety tower cases there often isn't enough airflow to cool all components effectively with a single fan, even going at full speed. And the single fan in the power supply was basically designed to cool the power supply, not the components in the case. This is why processors and some graphics cards have their own fans now.
A few years ago PCs often had two or more case fans in addition to the power-supply fan. This made sense in the era of 80mm fans and lots of expansion cards obstructing the airflow, but it was noisy. Nowadays, with sound and graphics and Ethernet integrated onto motherboards, expansion cards are much less common (and processors carry their own mini-fans). Thus, today's standard is to mount one 120mm fan, usually low and forward just beneath the disk-drive stack. This is much quieter, like by a factor of three or four.
The noise produced by a fan is not just a function of the speed with which it turns. It also depends on the nature of the airflow produced by the fan blades and the bearings of the rotor. If the blades cause lots of turbulent airflow, the fan produces lots of noise. One brand of fans that is much more silent than most others even if going at full throttle is Papst.
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:
(I used to have "Voltage, temperature and fan speed monitoring hardware." on this list. But processors run so hot nowadays that all current motherboards have it.)
The dominant form factor is still ATX. Intel tried to replace it with a new standard called BTX in late 2004-2005, but failed; the proposal was effectively withdrawn in 2006. In January 2007 AMD announced a DTX specification for small-form-factor PCs; it remains to be seen whether this will gain any traction.
The largest user-visible change since the last major update of this guide is that the CRT (cathode-ray tube) is dead. The manufacturers shut down their production lines in late 2004; the remaining CRTs out there are old stock that's been sitting in warehouses. The only reason to buy one since then has been to get high-end resolution at a price lower than the insanely expensive high-end flatscreens; with 1920x1440 flatscreens now (late 2007) becoming generally available at reasonable prives even that reason is gone. It's all flatscreens now, baby.
On flatscreens, only two statistics matter; pixel size and response time. The biggest functional drawback of flatscreens relative to CRTs is that they refresh more slowly, because cheical reactions in a flatscreen pixel take longer than remodulating a flying electron beam. You'll never notice this during ordinary desktop use, but it can cause streakiness and artifacts when you're playing games or viewing movies. If you're going to do that a lot, the price premium for a flatscreen with better response time may be worth it.
Next, buy your card (if you have to; see next paragraph). This used to be complicated, with issues like matching the video bandwidths of the card and the CRT, and the amount of display memory. Now (unless you are a gamer or have similarly extreme 3D acceleration requirements) it's simple; all cards have enough display memory for every resolution in use, and the issues are software (does it have an open-source driver, and do you care?)
It's actually fairly likely you'll never buy a video card again. Very capable graphics chips are routinely integrated onto motherboards now; unless you're a gamer or somebody else who absolutely must have the latest wheeze in 3D acceleration, they'll be good enough. Even this is not a stable situation, as 3D acceleration is commoditizing too.
I used to carry a lot of material on different video standards, interlacing, and flicker. That stuff is all obsolete now.
Here's what to look for on the monitor spec sheet:
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.
DVD drives have two main uses in computer systems: playback of video DVDs, and use for data storage (either installation media or backups, or even as a primary drive in a few specialized systems).
DVD burners (drives that can read and write CDROM media as well as several kinds of DVD media) are now low cost and useful. Most come with either a parallel ATA ("IDE") interface or, increasingly, a SATA interface. Linux and most current PC Unix-like systems will work fine with either interface. Given the choice, SATA is slightly preferable because the cable is smaller and simpler, and modern motherboards have more SATA connections than parallel ATA ones.
There is probably little or no benefit in seeking out a DVD drive with a SCSI interface any longer.
(Most of this section courtesy of James Turinsky.)
If you only need to watch video DVDs sold for and intended to be played in your own "region" of the world, you may skip this section.
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.
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:
If you are interested in multi-track digital recording, two particularly good choices are the M-Audio Delta, or RME Hammerfall series of cards. Decent (and lower cost!) two-channel cards for more normal use are those using the ICE1712 (Envy24) and ICE1724 (Envy24HT) audio chips. For normal users, though, almost anything will work fine!
A rather comprehensive list of sound cards and chips supported by the ALSA project, which is the main way sound cards are supported under Linux, can be found at ALSA Sound Card Matrix.
In speakers, look for a magnetically-shielded enclosure with volume, bass and treble controls. Some speakers run off the card's 4-watt signal; others are "self-powered", using batteries or a separate power supply. Your major buying choice is which one of these options to pursue. Usually you'll want separately-powered speakers. If appropriate for your listening habits, a pair of decent headphones will get you better quality sound for the money compared to speakers.
One final, important tip: that audio cable from your CD-ROM back to the sound card is used only when you play audio CD-ROMs through your speakers. Software-generated sound goes through the system bus, so you can play games with sound even if your sound board won't accept the audio cable connector.
Demand for (dialup telephone) modems is dropping as more and more people get broadband Internet through DSL and cable. This section still has as much detail as it does only because (a) there are people out beyond the exurbs who can't get broadband, and (b) there are one or two remaining traps for the unwary.
The modem market has stabilized and standardized. If you can spend $59, get a U.S. Robotics V.92 USB external. You can then know that you've got the best and skip the rest of this section. If you really must economize, spend $39 for the internal-card version (but you'll probably regret the $20 first time you have to do diagnostics).
The modem market is like consumer electronics (and unlike the computer market as a whole) in that price is a very poor predictor of performance. For ordinary file transfers, some $50 modems are better than some $150 modems. Paying top dollar mainly buys you better tolerance of poor connections and better performance at heavy-duty bi-directional transfers (such as you would generate, for exmaple, using SLIP or PPP over a leased line to an Internet provider).
In today's market all modems do a nominal 56kbps —V.90 and V.92 plus V.29 or V.17 fax transmission and reception (over plain old phone lines you won't get more than 53K of that). You don't see much in the way of slow/cheap to fast/expensive product ranges within a single brand, because competition is fierce and for many modem board designs (those featuring DSP (Digital Signal Processor) chips run by a program in ROM) adding a new protocol is basically a software change.
Most modems come in two packagings: internal, designed to fit in a PC card slot, and external, with its own case, power supply, and front-panel lights. Typically you'll pay $20 to $30 more for an external modem than you will for the internal equivalent. You'll also need a serial or USB port to connect your external modem to.
Pay that premium — being able to see the blinkenlights on the external ones will help you understand and recover from pathological situations. For example, if your Unix system is prone to "screaming-tty" syndrome, you'll quickly learn to recognize the pattern of flickers that goes with it. Punch the hangup/reset button on an external modem and you're done — whereas with an internal modem, you have to go root and flounder around killing processes and maybe cold-boot the machine just to reset the card.
See Rick's Rants for extended discussion of this point.
Don't buy a serial (RS232C) modem. This used to be the only kind there was, but they were always a bitch to configure and troubleshoot. Go USB instead; the sanity you save may be your own.
If the abbreviation "RPI" occurs anywhere on the box, don't even consider buying the modem. RPI (Rockwell Protocol Interface) is a proprietary "standard" that allows modem makers to save a few bucks at your expense by using a cheap-jack Rockwell chipset that doesn't do error correction. Instead, it hands the job off to a modem driver which (on a Unix machine) you will not have.
Also avoid anything called a "Windows Modem" or "WinModem", "HCF", or "HSP"; these lobotomized pieces of crap require a Windows DLL to run. They will eat up to 25% of your processor clocks during transfers, and hog high-priority interrupts (causing your machine to stall under Windows even if your processor still has spare cycles).
Many modems come with bundled Windows fax software that is at best useless under Unix, and at worst a software kluge to cover inadequate hardware. Avoid these bundles and buy a bare modem — it's cheaper, and lowers the likelihood that something vital to your communications needs has been left out of the hardware.
Avoid "Class 1" and "Class 2" modems. Look for "Class 2.0" for the full EIA-standard command set.
Fax capability is included with effectively all modems these days; it's cheap for manufacturers, being basically a pure software add-on. The CCITT also sets fax protocol standards. Terms to know:
There's a separate series of standards for software control of fax modems over the serial (or USB) line maintained by the Electronics Industry Association and friends. These are:
Class 1 — base EIA standard for fax control as extensions to the Hayes AT command set.
Class 2.0 — enhanced EIA standard including compression, error correction, station ID and other features.
Class 2 — marketroidian for anything between Class 1 and Class 2.0. Different "Class 2" modems implement different draft subsets of the 2.0 standard, so "Class 2" fax software won't necessarily drive any given "Class 2" modem.
There's also a proprietary Intel "standard" called CAS, Communicating Applications Specification. Ignore it; only Intel products support it.
There really isn't all that much to be said about printers; the market is thoroughly commoditized and printer capabilities pretty much independent of the rest of your hardware. The PC-clone magazines will tell you what you need to know about print quality, speed, features, etc. The business users they feed on are obsessed with all these things.
(There used to be a problem with "GDI printers" and "WinPrinters" that only worked with Windows —they required special drivers that took over your CPU to do image processing, These were such a bad idea that they have basically disappeared off the market.)
Most popular printers are supported by GhostScript, and so it's easy to make them do PostScript. If you're buying any letter-quality printer (laser or ink-jet), check to see if it's on GhostScript's supported device list — otherwise you'll have to pay a premium for Postscript capability! Postscript is still high-end in the Windows market, but it's ubiquitous in the Unix world.
Warning, however: if you're using ghostscript on a non-Postscript printer, printspeed will be slow, especially with a serial printer. A bitmapped 600 dpi page has a lot of pixels on it. At today's prices, paying the small premium for Postscript capability makes sense.
If you're buying a printer for home, an inkjet is a good choice because it doesn't use gobs of power and you won't have the toner/ozone/noise/etc mess that you do with a laser. If all you want is plain-ASCII, dot-matrix is cheaper to buy and run — if you can find one. Inexpensive ink-jets and lasers have almost driven them off the market.
Inkjets are great in that they're cheap, many of them do color, and there are many kinds which aren't PCL but are understood by Ghostscript anyway. If you print very infrequently (less than weekly, say), you should be careful to buy a printer whose print head gets replaced with every ink cartrige: infrequent use can lead to the drying of the ink, both in the ink cartrige and in the print head. The print heads you don't replace with the cartrige tend to cost nearly as much as the printer (~$200 for an Epson Stylus 800) once the warranty runs out (the third such repair, just after the warranty expired, totalled one informant's Stylus 800). Be careful, check print head replacement costs ahead of time, and run at least a cleaning cycle if you don't actually print anything in a given week. (Conversely, toner starts out dry, and ribbon ink won't evaporate for years...if you truly print only rarely, but neither a dot matrix nor a laser makes sense, consider buying no printer and taking your PostScript files to a copy shop...)
Nowadays, a lot of printers are moving away from parallel-port interfaces to USB. This is a good idea, because USB devices announce themselves to the host computer and can be automatically configured. Parallel ports (and serial ports for that matter) are becoming obsolete. Many new PC motherboards no longer include them.
Many printers (even some sub $100 models) now come with a network (10/100 Ethernet) interface. This make sharing them trivial, and also avoids having to leave a desktop PC powered on so others (using notebooks perhaps) can print to your printer. Therefore, such printers are worth considering in many networked environments, including home networks.
In the near future, new motherboards may stop including parallel and serial ports altogether. That's another good reason to go with a USB- or Ethernet-capable printer.
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.
(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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