Dave Patterson
by Dave Patterson
patterson@cs.berkeley.edu
Professor in Computer Science at UC Berkeley
September 25, 1998
While I was a grad student I worked at Hughes Aircraft on the computer for the radar system, starting in 1971 or 1972, so it brought back old memories.
Notice that he has lots of references to microprogramming in the document, which is typical of that era. (The aerospace computers I did were microprogrammed too.) The word “microprocessor” was used before the 4004 to mean the processor in a microprogrammed computer by some people of the time, so its not shocking to see the word microprocessor in a document of that era. In kind of used the term ambiguously, but it was a single chip CPU.
What this document describes is a microprogrammed set of custom LSI chips that can configured into multiple configurations and then microprogrammed, apparently in binary, to perform some application.
I think the minimum system is has 3-4 chips for the CPU, but I’m not positive from the stuff I read, but you could use many more to get more performance. It depends whether you include the ROM (microcode memory) and the RAM (“RAS”) as part of the CPU. Then it would be at least 2 more chips (5-6 total) in the CPU. Its plausible to include them since the RAM only had 16 words, so its like a register file, and the microcoded CPUs of the time would include the ROM in the CPU. His designed scaled, so there could also be lots more chips in his computer, without it being a multiprocessor. The designer just had to write the microcode that made it all work.
You should classify it as a microprogrammed special purpose computer, using a variable number of custom chips packaged as DIPs that could provide good performance in a small footprint. A classic aerospace thing to do, although most aerospace engineers of the time would design computers using standard TTL chips to reduce development costs.
I agree that its likely that the 4004 wasn’t fast enough; it had to fit into a single chip, and that meant sacrificing performance to make it fit. Holt’s used the technology to solve a fixed problem, and that problem wasn’t a desktop calculator (which led to the 4004) but signal processing for the F14A.
No way Holt’s computer is a microprocessor, using the word as we mean it today. Arguing that it is simply revisionist history, trying to claim a glory that isn’t deserved. Unless there is some patent deal going on, I don’t know why people would do this. Holt must understand the real issues; he looks to be a good computer engineer.
Hughes actually did a wafer-scale integrated CPU a couple of years later, which I worked on, and its was probably one of the first real ones, but who cares? There was no path from it to anything that had commercial impact, and its not like engineers at commercial companies were studying aerospace computers to get ideas to steal and put them in their commercial computers.
Dave
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