There is a popular misconception that AMD wasn’t good at cloning Intel CPUs. This is largely based on the observation that Intel released its 386 CPU in 1985, and AMD didn’t counter with its Am386 clone until March 2, 1991, nearly six years later. In this blog post, we will explore what took AMD so long, and how that delay played into future AMD CPUs.
Intel and its agreement with IBM
When IBM selected the Intel 8088 CPU to power its IBM PC 5150, IBM insisted on Intel licensing the design to at least one other chip manufacturer. This was to ensure that IBM would have a sufficient supply of chips to meet demand. It was also not a particularly unusual request. Both Apple and Atari had multiple sources for the chips they used in their computers, for instance.
Intel did IBM one better. Not only did they license the design to AMD, but they licensed it to several other companies as well. And after IBM selected the 80286 CPU to power its PC/AT, Intel amended the agreement with AMD and several others so they could manufacture not only 8088 and 8086 CPUs, but 80286 CPUs as well.
But the 386 was different.
It wasn’t just that Intel got greedy
The now-popular story is that with the 386 generation, Intel got greedy and decided to shut everyone out. At best, that’s an oversimplification of what happened. When Intel released the 80386 on October 17, 1985, IBM didn’t want it. Today this sounds absurd. Why would IBM not want Intel’s most advanced CPU?
In the mid 1980s, IBM still had a very lucrative business selling minicomputers. These were medium-sized computers designed for applications where a mainframe would be overkill but a PC wasn’t powerful enough. And IBM’s pricing didn’t scale linearly. Mainframes were the most profitable systems for IBM, and microcomputers–what we now call desktops–were the least. Minicomputers were in between.
IBM didn’t want the Intel 386 because it performed like a minicomputer chip. IBM could price its low-end System/36 minicomputers at $20,000 circa 1985, so they saw an Intel 386-based PC priced at $10,000 as a threat, not an opportunity. They didn’t want businesses buying a 386-based PC and loading Unix on it instead of buying a traditional minicomputer that cost twice as much.
That meant Intel had no reason to amend its agreement and extend the 386 to second sources. IBM wasn’t asking.
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