I draw a tutorial as a picture to explain (well I hope) how to pass from 3.3V to 5V on the CTPCI slot board for all PCI bus...
With that, you can use the FALSE UNIVERSAL PCI boards (VIO forced to 5V like a famous USB board)) and even some pure 5V designed boards IF you add the keylock on the edge connector... to be able to plug it on CTPCI, sure !
It will be put on my page later, when I'm sure it is working !
Yes, I did not test this workaround.If you test it, I'm be happy because I will not have to loose time to test it ;-)PS : PLX is OK for 5V tolerance.
Do the modification on all PCI slots... because if you still the Radeon on 3.3V IO mode and send to it some 5V signals, it may be slowly destroyed on PCI pins.