PCI-X, has the same pinouts as PCI. You have the extra connector for the
64bit version, and it can run at a faster clock. Pinout:
http://pinouts.ru/Slots/PCI_pinout.shtml
If instead you mean PCI-Express, then:
http://pinouts.ru/Slots/pci_express_pinout.shtml
PCI-X, has 5v available (even on the 3.3v versions, there are a couple of
5v pins), but PCI-Express,only has 3.3v for the logic, and 12v for things
needing higher voltages.
Best Wishes