The PCI-MXI-3 card is currently available only in one configuration - 5V, 32-bit/33Mhz PCI. The MXI-3 boards must be used in a 5V system, but it will interoperate with cards using 3.3V signaling. There is not a PCI-X version of the MXI-3 card at this time.
Regards,
Joshua Hernstrom
Applications Engineer
National Instruments