PCI-express or PCI-X, I don't know the difference and didn't know there was a difference. I'm a network guy not a hardware guy. I just remember the vendor saying PCI-express. I looked at the documentation for the card and all I got was that the LSI card will fit in both 32-bit and 64-bit pci slots.
Here is some good ready that may explain to you the difference in an easy way.
http://www.intel.com/network/connectivity/products/whitepapers/mesh_pcie_whitepaper.pdf Daniel
