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It acted as a control processor with a lot of different roles. For instance, it could handle the interface signals between an external computer and a piece of H
by kens 6y ago
It acted as a control processor with a lot of different roles. For instance, it could handle the interface signals between an external computer and a piece of HP test equipment. Or it could process button presses and control the display. Or it could parse ASCII command strings. With an external 74181 ALU chip, it could even compute error percentages in a voltmeter.
- bluu00 6y agocurious. any relevancy in modern technology?
- jdmichal 6y agoInterestingly, the $360 quoted in the article is not that far off from a modern desktop Intel chip. For $25 today you can get an entire computer in the form of a Raspberry Pi 3 A+. It was a cheap to manufacture chip with extremely limited capabilities. We certainly still have those, but the art has advanced to where the "extremely limited" part is not as limiting as it once was.
- bleepblorp 6y ago$360 USD in 1974 dollars is $1,892 in 2020 dollars, which will buy you a 32-core Threadripper 3970X today.
- jdmichal 6y agoThat doesn't really mean anything, other than the fact that the technology has gotten insanely cheaper. It's much more relevant to the question to compare the relative costs to modern chips. I just thought it was interesting that we could actually do this using things relatively close to the original price points in the article.
- egsmi 6y agoQuick question on the post, in the paragraph on metal gate transistors there are a couple of advantages listed. The last one says, "Third, metal-gate circuitry required an additional +12 V power supply." It's not clear to me why a +12V supply would be an advantage? Did 1974 have their equivalent of ATX supplies so that meant one less rail the PCB needed to generate compared to silicon-transistor designs? And there is some interesting cut in the ceramic that is exposing the lead frame on the left side of the package in the picture that is showing where the -2.5V bias note was written. Do you know what that is?
- jacobr1 6y agoThat is a disadvantage. > First, silicon-gate transistors were smaller, faster, and more reliable. > Second, silicon-gate chips had a layer of polysilicon wiring in addition to the metal wiring; this made chip layouts about twice as dense.8 > Third, metal-gate circuitry required an additional +12 V power supply. This implies silicon-gate chips DO NOT require the additional power supply.
- kens 6y agoAs jacobr1 pointed out, it's a disadvantage of metal-gate transistors, not an advantage. Silicon-gate transistors are entirely better than metal-gate transistors. (Except now metal-gate transistors are coming back for high performance, using "high-k" metals like hafnium. But these are completely different from 1970s-era metal-gate transistors.) For your other question, the visible metal trace on top of the IC package is a common thing with ceramic packages. I think the purpose was to ground the metal lid of the IC to protect against noise, static, etc.
- egsmi 6y agoOh, I see. I completely misread that paragraph. If the metal strip is on the top of the ceramic and grounded it makes sense that it would be for ESD protection. Especially as they likely did hand assembly of the PCBs.