GoKawiilIn The Virtues Of The 8-bit Era : Eight Iconic Processor Designs we looked at eight of the most important microprocessor designs of the 1970s and early 1980s. This time we’ll look at more 8-bit designs from that era, that didn’t quite make it into that list.
The rules are broadly as before. The designs have to be for microprocessors and not microcontrollers. They don’t have to have made it into production though.
Most of these designs didn't have a big impact, but just because they weren’t commercially successful doesn’t mean that they weren't interesting. And sometimes we can learn as much from market failure as from success.
So here are some lesser known ‘8-bit era’ microprocessors.
TMX-1795 (1971)
The first entry in the list comes from Texas Instruments. The team that created the first microcontrollers, led by Gary Boone, had earlier worked on a custom design for the Control Terminal Corporation’s ‘Datapoint 2200’ terminal which led to the creation of the TMX-1795 microprocessor. A little later, Intel created the 8008 using the same instruction set architecture.
The TMX-1795 is one of a number of designs that can reasonably be claimed to be the first microprocessor. Ken Sheriff has written about the 1795 and the contesting claims here. It’s a great blog post, and I’m not going to spoil Ken’s conclusions!
The TMX-1795 didn't even make it into production, but it did make an impact decades later. The design was used in the patent lawsuit between Gilbert Hyatt and TI.
The TI laptop has been modified to use the TMX-1795 for all operations. Everything displayed is being executed on a 1971 vintage 8-bit microprocessor. This demo unit was built in 1993 to be used as a jury exhibit in a patent lawsuit, although it was never used for that purpose. Its first public demonstration occurred a few days later, at the 1996 Microprocessor Forum, during the 25th Anniversary of the Microprocessor celebration.
We can see the TMX-1795 booting up in this Computer History Museum video.
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