<<<Well, actually the 8500 & 7500 motherboards are in fact different. The 8500 has better video-in, & it's got video-out on the motherboard. They're very similar, but not quite the same. Plus there's the slight fact that the 8500 has a PPC 604, whereas the 7500 has a PPC 601. I'm not sure if they built in 604 compatibility in the boot ROMs, and processor daughtrboard, but I wouldn't exactly count on it.>>>
As an owner of a 7500, I can tell you that the 7500 and 8500 motherboards ARE IDENTICAL. The video input/output is on a small card that is hooked to the motherboard through a connector (which is identical between the 8500 and 7500). If I could find it, I could conceivably buy the small (2"x3") circuitboard and put it in my 7500 and have the same video capability of an 8500 (minus the processor speed)...as long as the ROM would handle it, and I believe its supposed to. The Processor Card slot is identical as well. For instance, if I could find someone with a 8500/120 who is upgrading to a 150Mhz processor, I could buy their 604/120 card from them and simply put in my machine and restart...bingo all the power would be there. The ROMs are slightly different, basically differentiating the model for "About this Macintosh".
