Re: 6510 and 8500 differences

From: Nicolas Welte (
Date: 2000-07-30 11:43:01

Richard Atkinson wrote:
> I'm going to leave the C64C and C128D on all night. Depending on how low
> the 8500 result is tomorrow, it may be possible to arbitrarily set a
> 'reasonable' cut-off point between 6510 and 8500, but it would only be
> accurate after the machines have been on for some time and there would be
> the possibility of erroneously detecting C64s as C64Cs for recently turned
> on machines.

Thanks for all the measurements, Richard! I'm also quite amazed that we
have a temperature sensor in our CPUs, this is something that just
became popular with the Pentium III and it's integrated temperature
diode. We had it for 18 years! (But didn't know about it)

A bit more accurate measurements (cycle exact with the CIA timers,
connected to a 32bit timer) would be nice, but if there already is an
overlap between 8500 and 6510 values it doesn't really make sense. I did
some measurements of that kind already on the two SID types, but soon I
found one 8580 that wasn't much different from most of the 6581, so I
kind of stopped looking at more machines. I might have another go and
study the temperature dependenance, if it also affects the SID effect.
But then I would also include CPU measurements so I could get both
values at once.

Are there any more registers with unconnected bits that could be looked
at in a similar manner? I don't know of any such bits in the CIAs or in
the VIC-II.

> How well defined is the $DExx functionality difference between C64s and
> C64Cs? I feel sure we're on the right track, but will have to put in some
> considerable refinements to the process to achieve a high level of
> accuracy from the moment a machine is powered up.

In any case a machine type detection program must examine this
functionality, but I already said that a few (probably slightly damaged)
"C64Cs" fail this test. It also isn't a 100% sign for a 8500. 


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