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Episode 7 Notes - PC and the Clone

Jul 3, 2019

The IBM PC is, undeniably, one of the most influential computers of all time. It spawned a legacy that goes on to today. Nearly all computers in 2019 are descended from the PC architecture designed at IBM in the 1980s. However, a lot of its spread and rise to power came from outside of IBM. I'm speaking, of course, about PC clone hardware.

Computer manufacturers scrambled to get a slice of the market in the months following the spectacular release of the IBM PC. The PC was an mostly open platform: it used all off the shelf parts, and all the code and hardware design was published by IBM themselves. However, the BIOS firmware used to manage the low-level functions of the PC was copyrighted. So making a PC clone hinged on being able to circumvent the BIOS copywrite.

One of the issues I ran into while working on this episode was finding which computer was the definitive first PC clone. A lot of systems are touted as such, but I couldn't find much verification. It seems like the main issue is that most early clone manufacturers were startups or small companies, so only the successful ones like Compaq lived long enough to tell their story. Complicating that is the fact that some of the early clones used BIOS versions that weren't 100% PC compatible, but were advertised as compatible. Others just plain copied IBM's BIOS and were sued over it, such as Eagle and Cordata. The closest I could find to an answer was the Columbia Data Products MPC 1600. That machine was announced in June of 1982, and supposedly had a 100% compatible clean room BIOS. You can even find dumps of it's firmware and run/test it yourself. However, I couldn't find sources confirming much for that computer, or information on it's design process.

In a "history is written by the victors" type of thing, Compaq has really good documentation of it's PC clone. There is a lot of writing on the Compaq Portable's design process from both in and out of the company. FThe book "Open: How Compaq Ended IBM's PC Domination and Helped Invent Modern Computing" written by Rod Canion, Compaq's co-founder, provides a good narrative of the creation of the Portable including the clean-room BIOS development process. However, it may not be the most neutral source since it is from within Compaq. One thing of note that ties into the muddied waters of PC compatibles in this era is that Rob mentions the MPC 1600 in passing as a incompatible PC clone.

Once we get out of the 1982/1983 era, the clone market starts to be a little easier to parse out. Partly because all the major players are already established. This is also when Phoenix Technologies hits the scene with their licensable BIOS. Phoenix created a similar clean-room BIOS to Compaq but used a few more safety measures. Their BIOS was written by one programmer who wasn't familiar with the x86 architecture, and Phoenix kept a paper trail of memos with all the information that developer had access to. There are also pretty good primary sources on Phoenix, mainly in the form of articles written around the time their BIOS was released(,

If you want to hear more of my take on the early era of PC clones and how it changed the computer market, here is my episode covering it:

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