>Does anybody know how to determine if a machine has a processor upgrade card
>in it (as the control panel does)?

If you are talking about the 68k to PPC upgrade card, this is probarly 
detected by indexing throught the NuBus slot list, looking for a card 
with a certain ID or name.

If you are talking about the PPC with a processor on a daughter-card, I 
think you will find its all done in hardware, so that it is transparent 
to the machine & OS.

Jamin