4 ms·

A PLA is reasonably space-efficient if you need gates with a fixed set of inputs and outputs. Even the 8008 used one for instruction decoding. In addition to th

by kens 6y ago

A PLA is reasonably space-efficient if you need gates with a fixed set of inputs and outputs. Even the 8008 used one for instruction decoding. In addition to the microcode ROM, the 8086 has several PLAs of various sizes. For instance, one PLA converts the ALU operation into the necessary ALU control lines.

NortySpock 6y ago
It would also be fast, right? You would only need to worry about transistor switching speed, not decoding microcode... Disclaimer: just a software engineer, I've only ever heard of microcode, never seen it or written it.
- Koshkin 6y ago
  Here's what I think is an excellent introduction to the subject (although it leaves unclear the distinction, if any, between microcode and PLA): https://people.cs.clemson.edu/~mark/uprog.html https://people.cs.clemson.edu/~mark/uprog.html
  - kens 6y ago
    A key distinction is that in a ROM, only one row is active at a time. But in a PLA, multiple rows can be active simultaneously.(This is from "The Architecture of Microprocessors".)
    - Koshkin 6y ago
      Makes sense, thanks.