4 ms·
I think it's not an accident that the two most successful ISAs today are x86, one of the simplest of the CISC ISAs, and Arm which was the most complicated of th
by Symmetry 4y ago
I think it's not an accident that the two most successful ISAs today are x86, one of the simplest of the CISC ISAs, and Arm which was the most complicated of the RISC architectures. Arm 64 has reduced that complexity somewhat by getting rid of things like universal predication but they've still got instructions that, e.g., store or load two registers in a single instruction.
- AnimalMuppet 4y agoUm, what CISC ISAs do you think are more complicated than x86?
- Symmetry 4y agoI'm going from John Mashey's famous Usenet post on the issue. https://userpages.umbc.edu/~vijay/mashey.on.risc.html https://userpages.umbc.edu/~vijay/mashey.on.risc.html So that would be things like Vax that not only have load-store opps, they also have things like indirect loads and stores in a single operation.
- klelatti 4y agoS/360 and it’s successors
- fanf2 4y agoS/360 is also a relatively simple CISC. The more complex ones (many mem-mem instructions with fancy addressing modes) are VAX, 68020, NS32000.