The 7500 and 7600 are similar enough in motherboard design (all the same type of parts in the same places) that they can be considered identical, however, they are not actually so. They are indeed different part numbers. In fact, some claim that the 7500 has a higher tolerance for overclocking the bus than the 7600 as a function of the difference in part quality between the two models...

They also share the same case design that was common to the 7200, 7500, 7600, 7300, and desktop G3 (slight case mods to accomodate the personality card).

Regardless, virtually any CPU ugprade that works in the 7500 will work in any PCI-class Power Mac including the 7600, 8500, and 9600.

Peace,

Drew