4 ms·
The 6502 is not microcoded, or at least not in the way we presently conceive of microcode. Its operations are driven by an on-board PLA which controls decoding
by classichasclass 4y ago
The 6502 is not microcoded, or at least not in the way we presently conceive of microcode. Its operations are driven by an on-board PLA which controls decoding and sequencing with its gates, which also explains its high performance per clock. It would be hard to call those gate connections micro-opcodes since they're not really used in that sense.
- sroussey 4y agoI did say it was weird… ;)
- colejohnson66 4y agoThe 6502 uses "horizontal microcode", which, as you said, are the individual control lines. x86 uses "vertical microcode" which is a sort-of internal RISC architecture.