Re: 6510 and 8500 differences

From: Richard Atkinson (
Date: 2000-07-29 02:25:04

Some preliminary results with a C64C, C64G and a C64. The C64G produced
the expected $80, 0, 0 result and the C64 started with $00 and the msb in
the 190s. As the machine warmed up the msb reduced to figures in the 40s
before I unplugged it and tried the C64C. Again, like the 'G, it produced
$80, 0, 0 so I left it on to see if the routine would stop timing out and
start producing some high bytes in the 250s.

Sure enough, every now and then a result started appearing that said $00
and something in the 250s, sometimes 240s, although initially there were
still lots of $80, 0, 0. Now, however, it's producing results consistently
in the 190s having decreased all the way from 255. I'm going to leave it
on overnight and see just how low it gets, but I suspect what we have here
isn't a 6510/8500 detect routine but a CPU temperature sensor!

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.

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.


Richard Atkinson
Software Engineer
Tenison Technology EDA Ltd

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