FPGA luminary David Laws has just published a well-researched blog on the Computer History Museum’s Web site titled “Who invented the Microprocessor?” If you’re wildly waving your raised hand right now, going “Ooo, Ooo, Ooo, Call on me!” to get teacher’s attention because you think you know the answer, then you don’t understand that it’s a trick question. It all depends on how you define the word “microprocessor,” doesn’t it?
According to Laws, there is no lack of good candidates:
Four Phase Systems 8-bit AL1, first demonstrated in working systems in April 1969. (Industry gadabout and processor expert Nick Treddenick’s pick.)
Ray Holt’s 20-bit MP944 custom chip set, developed for Garrett AiResearch’s Central Air Data Computer for use in the F-14 Tomcat fighter jet’s flight-control system, and first manufactured in 1970. (Note: This was not a single-chip microprocessor, but it was a microprocessor by some definitions.)
Intel’s 4-bit 4004, originally developed in early 1971 as an implementation mechanism for Busicom’s line of calculators and first advertised as a commercial microprocessor in November, 1971.
Intel’s 8-bit 8008, originally developed for the CTC/Datapoint 2200 Programmable Terminal and delivered in late 1971.
TI’s 8-bit TMX1795, another implementation of the CTC/Datapoint 2200 Programmable Terminal processor, delivered to CTC a few months before Intel’s 8008, but with a design bug caused by an error in the original processor definition.
So there you have it; it’s a trick question. Do you include multi-chip processors? If so then the MP944 is your pick. If it has to be a single-chip processor but need not have been sold as a commercial chip on the open market, then the AL1 might be your choice. If a calculator processor that ended up opening the era of embedded system design qualifies, then the Intel 4004 is your answer. If a “real”-but-flawed, single-chip processor that didn’t meet the customer’s intended spec qualifies, then TI will get your nod. If none of these, then you’re an Intel 8008 booster.
This is not merely an academic exercise. There has been plenty of patent litigation attached to the answer to this question.
I’ve been dancing on the head of this pin a long time as an editor and industry historian. For my money, the first commercially successful microprocessor, the one first sold on the open market to design engineers, is Intel’s 4004.
You can put your hands down now. Class is no longer in session.