Running a Performa 6300 Mobo in a Power Mac 6500 case?

[ry755]

Hey all, I have a Performa 6300CD motherboard that has been sitting in a drawer for a few years and I'd like to plug it in and play with it. I *did* previously try running it in my Power Macintosh 6500 case and it worked fine, but now that I think about it, I remember reading somewhere that mixing NuBus and PCI cases and mobos is bad because the power pins on the harness are slightly different, but now I can't find where I read that. Is this true? I'd rather not fully open up the 6500 case to check unless needed. If so, why did it work fine when I tried it previously? I'm mostly just asking to calm my fears of running this older mobo in the newer case and accidentally damaging it over time even though it did seem to work fine. (Yes, I know this is a downgrade, I'm just doing this for fun)

 

[Daniël]

I believe the main difference is that the 6500/5500/TAM Gazelle board, like its Alchemy 6400/5400 board predecessor, has a 3.3V rail, where the earlier boards in this form factor do not. You can see the pinout of the power section of the edge connector here (red = 5V, yellow = 12V, orange = 3.3V, and black = GND):



Do not quote me on this, but I think the 3.3V pin on the earlier boards is not connected to anything, so the 3.3V ends up not going anywhere. I don't know what the long term effect is of having no load on the 3.3V rail of the 6500's PSU, though.

 

[cheesestraws]

You might want to look at some of the Takky resources out there, they have a certain amount about wiring up these logic boards to things they're not meant to go in

 

[ry755]

Interesting, thanks both of you! That explains why it wasn't shorting 3.3v to ground like I half expected it to.