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It's interesting reading how the 6502 has a "Decode ROM PLA" that fires off various parts of the instruction its executing. It's a very primitive microcode. I
by tenebrisalietum 9y ago
It's interesting reading how the 6502 has a "Decode ROM PLA" that fires off various parts of the instruction its executing. It's a very primitive microcode. It would be interesting if that was customizable in an FPGA version or if the Javascript version allowed that to be changed.
- phire 9y ago"primitive microcode" is the wrong way of thinking about it. Microcoded CPUs had been around for ages by that point. It's a highly optimised microcode, designed to produce the correct control signals in the minimum amount of space while not caring about the output for illegal opcodes.