Re: MOS 8500 CPU for C64C

On Wed, Aug 30, 2023 at 3:38 PM <silverdr_at_srebrnysen.com> wrote:
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> > On 30 Aug 2023, at 12:51, Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de> wrote:
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> >>>> I know the 8500 CPU for the cost reduced C64C is rare would anyone here
> >>>> have any extras I could get?
> >>>
> >>> You can also use a 6510 from an older C64, they are compatible.
> >> Just the HMOS(II) vs NMOS apply to those two, right?
> >
> > Yes, the only difference is the process. I have seen 250425 boards with 8500 CPUs.
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> Yeah, /me too. And I know they're functinally the same but as we know CSG did various things with the numbering like marking the HMOS CIAs with NMOS number. Although doing it the other way around (like putting 8500 on a 6510) would make even less sense I guess ;-)

FWIW, 8500 vs 6510 can be detected in software by checking how many
cycles it takes for the unconnected port bits to decay from 1 to 0
level when the DDR is switched from output to input.
I made a test ASM for proof of concept years ago. The decay time is
also temperature dependent, but the 8500 is some (binary) order of
magnitude slower due to probably much better gate insulation and lower
die temperature (gate leakage depends on temperature).

Frank