Personal Computer

Design Examples > Maintainable Products

The ubiquitous personal computer enjoys an unusual status. Today, the IBM-compatible PC is by far the most complicated product in mass production, yet it is also one of the most easily repaired. Because of its modular construction, and because of large-scale standardisation between manufacturers, the availability of spare parts for PCs is unrivalled, and it should never be necessary to throw away a PC because spare parts cannot be found.

Introduced in 1981, the original IBM PC (designated model 5150) was IBM's attempt to make a late entry into the market for economical desktop computers, which was at the time dominated by the Apple II. The urgency with which IBM wanted to enter the market caused them to take two key decisions which have shaped the development of computer hardware ever since. Firstly, IBM needed to develop the computer in just one year, which didn't allow enough time to develop all the necessary components from scratch, so they bought off-the-shelf parts from other manufacturers. This limited the extent to which components could be integrated - that is, combined or merged to form single components which may be smaller and cheaper, but are generally harder to replace - and resulted in the PC's modular design. The CPU employed was an Intel 8088, the floppy drives were supplied by Tandon and the RAM by NEC. When hard disks were introduced to IBM's PC range, these were bought from Seagate. The IBM PC's operating system, MS-DOS, proved to be the making of Microsoft, but that is another story.

The second key decision was to employ an open architecture - that is, IBM published technical specifications for the machine so that competitors could manufacture and sell clones. The idea was that by involving other manufacturers the PC would be adopted more rapidly, and IBM could make a profit from licensing the machine's BIOS, the full details of which were kept secret. The BIOS (Basic Input-Output System) is the most basic level of software which runs on the computer. It provides an interface between the operating system and hardware and loads the operating system into RAM when the computer is switched on. It also accepts input from the keyboard and provides a primitive display on the monitor, allowing the hardware to be configured when the PC is first assembled or when new hardware is added. The BIOS code is normally stored on a chip which plugs into a socket on the computer's motherboard.

Unfortunately for IBM, the evolution of the PC didn't quite follow their plan. It was rapidly adopted, but a number of competitors (starting with Compaq) reverse-engineered the BIOS to create their own royalty-free versions. IBM fought back by releasing the higher performance PC XT (eXtended Technology) and PC AT (Advanced Technology) machines, and with these established the XT and AT standards for motherboards, power supplies and cases. The use of an open architecture for the PC was instrumental in triggering explosive growth in the PC industry during the 1980s and '90s, but it also meant that IBM gradually lost their dominance, and they withdrew from the PC market entirely in December 2004.

Today the whole computer industry (encompassing Macintoshes, Suns and various other types of hardware besides PCs) is very largely based on open standards. IBM's original x86 processor standard has been revised and expanded several times, the ISA, PCI and AGP standards for expansion and graphics cards have been released, and Intel has developed the ATX (Advanced Technology Extended) standard to replace the XT and AT standards. Many hundreds of other open standards exist for both hardware and software. Some of these standards (such as FireWire) require that a licence fee be paid to the inventor whenever a product utilising the technology is made, whereas others (such as Ethernet) may be used without charge.

We have IBM to thank for the abundance of economical PC components on the market today, and the ease with which PCs can be repaired. Standardisation is such that a broken component need not be replaced by an identical component; a component from any manufacturer which complies to the relevant standard will suffice. It is ironic, then, that computer technology has advanced at such a rate in recent years that many PC components become obsolete long before they fail. But the PC's design offers a solution to this problem too. Because of the almost universal adoption of the ATX standard for motherboards and cases, the PCI standard for expansion cards and the VGA standard for monitors, it is simple to upgrade a PC and improve its performance without replacing it. With the slow-down in the advancement of computer technology, there is the opportunity for the PC to become one of the most durable and long-lived technology products, but it is down to the consumer to make it happen.

For those who are interested in building a maintainable PC, here are few suggestions:

Don't base your machine on a big-name base unit such as a Dell or Compaq. These often employ non-standard motherboards and power supplies which are more difficult to replace or upgrade.
Build a computer which you like and does what you want from the outset. That way you're less likely to want a new one. If you're not sure what you want, talk to a few people and try using different systems to see which you prefer.
Choose a robust, good quality case which is easy to open. You should view the case as central to your system; a cheap case is a false economy. If you're going to maintain your PC, you need to be able to get inside it with a minimum of fuss. I've lost count of the number of times I've become frustrated trying to squeeze a flimsy case back together after upgrading a PC. The plastic on poor quality cases also tends to crack and turn yellow, and stripped screw threads are common.
Buy a keyboard and mouse which you like and find comfortable to use.
Buy the best components you can afford. Not only will they become obsolete less quickly, they are also less likely to fail or have compatibility problems.
Try running Linux or UNIX on your PC. These operating systems offer much better performance on older machines than Windows and can be customised to suit your needs. If, like me, you're interested in learning how things work, you'll be able to get much closer to the workings of your computer too.
If you don't need a high specification machine, you may be able build a machine from other people's discarded hardware. Some people - large organisations in particular - have got into the habit of upgrading their machines every few years, even when it isn't really necessary. Check out skips and bins near corporate premises and now and then you'll find a gem. Although not a PC, my computer was acquired in this way. Thank you, CUED!