[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: 6502 illegal opcodes questions

Am 17.05.2006, 17:31 Uhr, schrieb <heuser.marcus@freenet.de>:


Huh? They did move forward. 6510 -> 8500 -> 8502.


And what exactly were the differences between these chips?


8502 allows 2 MHz and afaik also has some extra pins for zeropage
addressing mode and stack detection.

8500 is ofcourse basically a 6510 :)


And also, I don't think it's any kind of problem for Commodore to use
customized CPUs since they owned MOS, the owners and producers
of 6502 tech back then :)


And, yes, MOS made all the funky custom chips - but the 6502-core chips
were AFAIK the most advanced CPUs designed/modified/produced by them.


The VIC or SID are about 3 times bigger than the 6502. But ofcourse the
6502 is ingenious :) the only bad thing about it is, that they wasted
transistor space for something like BCD mode. I would have preferred
some small extra commands like ADD without carry or TXY.