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A comment on The C64 Mini Computer. Parent comment

Re:The C64 Mini Computer by boomlinde on Friday September 29, 2017 @02:15PM (#15367653)
AFAIK, you can't buy new 6502s any more (nor can you buy the 6510 actually used in the C64). You can buy 65c02 chips, but those are slightly incompatible with the 6502 and 6510 on the opcode level.
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Re:The C64 Mini Computer by jhbadger on Friday September 29, 2017 @08:55PM (#15370514)
Not really significantly though. The Apple //c (and some ][es) had 65c02s rather than the 6502 in the ][ and ][+, but they could still run all the old software.
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Re:The C64 Mini Computer by boomlinde on Sunday October 01, 2017 @01:21PM (#15378776)
There are undocumented opcodes that still perform useful operations on the NMOS 6502, for example loading the A and X registers simultaneously, decrementing and comparing memory, along with a variety of more exotic instructions that can replace quite long sequences of equivalent "valid" opcodes. These are NOPs on the 65c02.

I know little about the Apple 2 series, but in quite some C64 software, these operations are used wherever they can save a few cycles. Mostly demos.

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