Re: 6510 and 8500 differences

From: Martijn van Buul (
Date: 2000-08-10 14:27:52

MagerValp wrote:
> ... but they also depend on the amount of electricity inside the chip.

Hmm. Nice way of putting it.. May I have two litres of electricity
please :)

Here I am, thinking that computers always work on smoke! When the smoke
gets out, it doesn't work anymore..

Joking aside, I wonder if there really is a (reliable, not exemplaric!)
connection between those 'nybble'-registers and the temperature of the
VIC. I don't know the VIC internals *that* good (Not on a silicon level,
anyway), but for the moment I'll assume that the higher nybble of the
VIC internal databus is just left floating when reading these registers.
This would mean that the logical levels of these individual bits are 
caused by parasitic capacities, and could be dependant of the *previous*
data passing through the databus, the actual layout of the chip, internal
pull-up or pull-down resistors, and the used logical family. A higher
temperature *could* lead to a higher chance to read a 1 (With higher
temperatures, the conductance of semiconductors slightly drops. This
includes (parasitic) conductances of the databus to ground, which
would mean that the databus could remain charged for a longer period.

I would't trust this method of measuring temperature - Differences
in individual chips could cause quite different results.

    Martijn van Buul - -
		Visit OuterSpace: 3333
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