Again, a wealth of information.
This, from my G5 service manual was what mad me nervous...
"*The PCI slots can accommodate mixed-voltage (5.0 V, 12 V, or 3.3 V) cards but only at
3.3 V signaling (huh?), with 32-bit or 64-bit data widths and a 33 MHz frequency. You can add a
66 MHz card to a...