toms explains pci-xPCI-X vs. PCI-expressPCI=X, PCI and PCI=E I only browsed this quick, but I believe it will help you see.. PCI-X is a standard different from PCI-express..It seems that the throughput on the pci-x is equivelant to an AGPx2. The difference is it's 64bit capable at 66mhz offering 533MB/s and is downward compatable with all pci cards. PCI-express is much faster