Its from Dell Precision Workstation 670.
" 3x high-end PCI-X slots"
I found this also:
"Matrox says that a 64-bit, 66 MHz PCI card is compatible with PCI-X slots and can run at 66 MHz in such a slot. So it seems like if I get a 64-bit, 66 MHz PCI card and put it in one of the three PCI-X slots...