If you maintain an interest in vintage computers, you may well know something of the early history of the microprocessor, how Intel’s 4-bit 4004, intended for a desktop calculator, was the first to be developed, and the follow-up 8008 was the first 8-bit device. We tend to like simple stories when it comes to history, and inventions like this are always conveniently packaged for posterity as one-off events.
In fact the story of the development of the first microprocessors is a much more convoluted one than it might appear, with several different companies concurrently at the forefront of developments. A fascinating recent IEEE Spectrum piece from [Ken Shirriff] investigates this period in microprocessor design, and presents the surprising conclusion that Texas Instruments may deserve the crown of having created the first 8-bit device, dislodging the 8008 from its pedestal.
The piece looks at the development of MOS integrated circuits for general purpose computing in the late 1960s, and the progression through a series of military and avionic, then mini- computers with ever smaller chip counts. Long-forgotten companies like Viatron, whose claim to fame is coining the word “microprocessor”, and Computer Terminal Corporation (CTC), whose Datapoint 2200 intelligent terminal was the seed for Intel’s 8008 architecture make an appearance. It was the Datapoint 2200 that lay at the root of TI’s claim for the first 8-bit microprocessor, both TI and Intel worked separately on processors to replace the 2200’s discrete chip processor. TI’s offering, the TMX1795, was completed months before the 8008, but in the event CTC rejected both chips and continued with its discrete architecture. Intel successfully commercialised the 8008 while the TI chip failed to find any customers, and the rest, as they say, is history.
The IEEE Spectrum piece investigates this period in extremely interesting detail, and is well worth a read.
We’ve covered the early Intel processors a few times in the past. We had an investigation of the 4004 internals, a Retro Challenge entry of a 4004 ROM emulator, and someone made a clock based on an 8008.
4004 die image: Intel Free Press [CC BY-SA 2.0], via Wikimedia Commons.