Posted By
TLC
on 2010-08-28
13:00:46
|  Re: CPU replacement?
Christian: I'd do that  , but I'm afraid I'm not much of practical help here. Replacing the 8501 by a 2-MHz 6502 + some glue logics should be possible, but neither I have made any attempts to do that.
A 6510/8500 base should impose the problem of a missing portbit... it should be also relatively difficult to supply the missing portbit "retroactively".
The 8502 might be a better candidate for the project, as it's a 2MHz 6502 descendant (the 6510/8500 might or might not work at 2MHz at all -- at least, they're not rated for 2MHz), and as it seems to have a 7-bit onboard I/O port. Problem: it appears to be almost as rare as the 8501 is by itself (...but I might be wrong in that assumption; honestly, I've never owned a working C128 myself, only some wrecks +a partially working one that I never really used).
At the end, neither I did come up with a solution -- I used what I had (cannibalized some 8501s from wrecks, and/or some of my own 264 series computers that I rarely used, in favor of those that I used more frequently), until someone on this forum pointed me to some Hungarian supplier that still had 8501 processors (...20 years old stock) for sale.
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