Matrox Odyssey XG Installation And Hardware Reference page 22

22 Chapter 4: Matrox Odyssey XG hardware reference
The maximum transfer rate between Matrox Odyssey XG and the Host is
determined by the maximum transfer rate between the SIB and the 256-bit GPU,
which is 528 Mbytes/sec when the Matrox Odyssey board is used with a PCI-X
slot. Matrox Odyssey XG can also be used with a conventional 3.3 V PCI slot, in
which case the maximum transfer rate might be reduced, depending on the
frequency of the PCI bus (132 Mbytes/sec for a 33 MHz 32-bit PCI slot, 266
Mbytes/sec for a 66 MHz 32-bit PCI slot, 528 Mbytes/sec for a 66 MHz 64-bit
PCI slot).
Using the PCI/PCI-X bus, Matrox Odyssey XG can also access Host DMA
memory (physically contiguous, non-paged memory). An advantage of DMA
memory is that a bus mastering device (such as Matrox Odyssey XG) can access
this memory without the help of the Host CPU.