The Surprising Story Of The First Microprocessors

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.

16 thoughts on “The Surprising Story Of The First Microprocessors

  1. My first micro was an 8008 which I designed and wire wrapped from scratch. In school for EE we didn’t have any micro classes so all I learned about micros was programming the chip and learning how to do it the hard way.

    BTW it was a dog of a chip with all the address and data lines going through the same 8 lines so you had to capture the high level address then the low level address then the data. That made it very slow. Even though the chip was small the supporting chips were large.

    1. Did you splurge on the hardware to add a stack? At least, I thought it was the 8008 that had no internal stack, an article in an early issue if Byte showed how to add a small stack.

      Michael

      1. Gosh it was so long ago, but it did have a internal stack, Online it said “Seven-level push-down address call stack. Eight registers are actually used, with the top-most register being the PC.”

      1. Damn, didn’t realize they came in that package. There is a nonzero possibility that I have one sitting in a box of junk somewhere, thinking it was some old 4000 series CMOS that I’ve never been big into using.

  2. Ahh the 8008. I helped debug code on one of those back in the late 70’s (?). Our memory board (4k bytes) was the size of a modern day laptop and was kept powered on 24/7 while debugging because the only way to reload it was via paper tape / teletype. The final debugged program image was then sent out of house and burned into a prom. Good memories.

    1. In the early days of silicon chips a fab could start producing 100% rejects for no apparent reason, so anyone who wanted chips in volume insisted that there be at least one second source. AMD got their licence for x86 from starting out as an official second source for example.

  3. National Semiconductor was the only second source company for the Intel 4004. The company announced second-sourcing of 4004 family at the beginning of 1975, started shipping samples in December 1974 – January 1975, and full production started in May – June 1975.

  4. I built the Mark 8 computer which used an Intel 8008. Had a 5-bit baudot teletype, a TV typewriter, and Dr Suding’s cassette interface. These were a good introduction to digital electronics, machine programming, and the peripherals, including the ever popular programming of serial data (AKA bit-banging).

  5. I’m glad to see Ken Shirriff’s detailed article. The evolution of the microprocessor from it’s calculator and terminal roots is a complicated story.

    Only in Intel’s corporate, loud, and constant re-telling of the story is Intel protrayed as the sole inventor. Hoff and Mazor deserve plenty of credit, but in Intel’s version, Faggin is all but written out the of the story…along with anybody else…at any other company.

    “History is written by the victors.” as the saying goes.

  6. Lordy, lordy, lordy, I worked for Data Point back in the day. They had a networking protocol called ARCnet way before ethernet ever got off the ground. The tech people begged upper management to license it out and beat ethernet to the punch, but of course…..The company was finally destroyed by Asher Edelman who raided the employees retirement fund and broke up the company.

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