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The Modcomp computer, 1970+, had a dynamically programmed instruction set capability using a programmable ROM. It was targeted at applications written for other
by jbottoms 8y ago
The Modcomp computer, 1970+, had a dynamically programmed instruction set capability using a programmable ROM. It was targeted at applications written for other systems, and for realtime problems that benefited by an instruction set crafted for a specific problem.
- Vogtinator 8y agoSomewhat like the Xerox Alto, which basically had an entire OS in microcode to provide CPU functionality.
- monocasa 8y agoI've heard the argument from a few chip designers that the main thing the user microprogrammable machines got you was a Harvard architecture. You got most of your wins by pushing complex ideas into ucode where each step fetched from the ucode ROM instead of the main memory bus. That's why on pretty much every microcoded machine you see a memcpy instruction. It's the most obvious win for getting the ifetches out of the way of your data throughput. Once we started adding instruction caches, that big win started to not be as big. Ultimately it's the caches that killed off that machine, and the ucode interpreters you saw on the Smalltalk and Lisp machines. One idea I would like to make it's way from ucode that hasn't yet though is being able to define interrupt boundaries for the real time tasks you allude to.