Why are Intel Corp and Microsoft Corp so big today? The answer is simple: because there are so many IBM AT-compatibles sitting on people’s desks out there. Why are there so many compatibles about? Because there are so many clone makers. Why so many clone makers? Because when IBM launched the original Personal Computer in the 1980s, there was no such thing as a standard, but the three letters ‘I.B.M’ on the front of the box meant here was a machine that would appeal to corporate buyers. And so the IBM Personal Computer spawned an entire industry, and at the same time ensured the success of the Intel iAPX-86 processor family and a klugey operating system called MS-DOS. In the early days, people failed to recognise that runs MS-DOS and IBM-compatible did not mean the same thing, and companies like Applied Computing Techniques Ltd – later Apricot Computers Plc, now ACT Group Plc – made tidy fortunes selling incompatible MS-DOS machines – not least because the Personal Computer was launched in September 1981, but IBM gave it such a low priority that the thing was not even launched in Europe until January 1983 – before the penny dropped, and the company realised it had to go IBM-compatible or die. Clone-makers turned out to be a mixed blessing for IBM – although they stole sales, they actually grew the total size of the market beyond IBM’s wildest dreams, even if IBM didn’t see it that way in the early days: Compaq Computer Corp is about the only survivor of the first generation of clonemakers. Instead of going after the right target – Microsoft – and renegotiating its agreements so that it owned MS-DOS (almost any price would have been justified but IBM was frightened of the US Justice Department), IBM saw almost all the other clonemakers off with vicious lawsuits, only to see a hardier breed led by the likes of Dell Computer Corp and AST Research Inc take their place. So when IBM conceived the PowerPC and pondered how to conquer the desktop, it decided to try the same trick again – but this time, by officially supporting clone production.
By Chris Rose
The PowerPC Reference Platform is a cloners charter. It is PReP to its friends, but the shortened form is publicly eschewed by IBMers since it is registered as a trademark by another organisation – a non-for-profit organisation in California apparently – though even the high-ups in IBM’s Power Personal division aren’t clear on this. Where cloning an AT is still a hit or miss affair – there is still no formal definition for an AT bus, for example – PReP codifies in detail exactly what a system designer has to do to ensure compatibility. The goal is to ensure software and peripheral compatibility between systems. PReP currently encompasses everything from laptops to multi-processor servers and will expand to cover personal digital assistants in the future. Its remit runs to four areas of system design: 1. Hardware Configuration: defining the minimum and recommended hardware standards and capacities required to be PReP compliant.2. Architecture: describing the minimum and recommended hardware system attributes.3. Machine Abstractions: this section sets out the minimum set of hardware features which each operating system and hardware system vendor has to abstract. It also outlines how software should cope with the variations in hardware between PReP-compliant machines. 4. Boot Process and Firmware: even before the operating system takes control of the machine, the personal computer has to run Boot software installed in ROM. PReP defines what is expected from this code. It does not, however define a universal BIOS in ROM, thus avoiding operating systems being tied to a single interface. Finally, IBM has gone to the trouble of providing a reference implementation, the full specs of a sample, working machine, which aspiring cloners can copy wholesale, if need be. In creating PReP, the partners trod a fine line – making the specification tight enough to ensure applications compatibility, while building in enough flexibility to enable competing manufacturers to differentiate t
heir machines.
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