7 ms·
> not microcoded Still microcoded, just not updatable. https://news.ycombinator.com/item?id=21428905 https://news.ycombinator.com/item?id=21428905
by twisteriffic 4y ago
> not microcoded
Still microcoded, just not updatable.
https://news.ycombinator.com/item?id=21428905 https://news.ycombinator.com/item?id=21428905
- monocasa 4y agoSo I've reflected on my previous statements there, and have come to the conclusion that the 6502's PLA isn't microcode or a compression format for a microcode ROM. The big piece it's missing is the microinstruction address counter. There was a T state counter which was tripping me up, but having played with the visual 6502, the T state counter really isn't a full microinstruction addr counter. The PLA is really more logically like individual CAMs for each of the control lines looking at the instruction register and the T states. So the PLA really is more an encoding of random logic than a microcode ROM. They end up being really close concepts though. A great case of 'that guy that inhabited this same body a few years ago was a fucking idiot and needs to learn to shut his mouth'. I'm sure the person to inhabitant this body in a few years will say the same about me.
- klelatti 4y ago> So the PLA really is more an encoding of random logic than a microcode ROM. Thanks for a very succinct summary of a question I've pondered for a bit too.