Well if my memory serves me, the motherboard designs between the 8500 and the 8600 are big enough to make me believe that the switching of the upgrade cards would be unsucessful if not dangerous to the machine. I would wait till an expert here can answer your question here. Personally I wouldn't try it.
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Paranoia-
You only have to be right once to make it all worthwhile
-Unknown
[This message has been edited by The Dude (edited 11-02-2000).]