Peripheral Component Interconnect – Extended

PCI-X is a hi-performance motherboard slot type created by HP, IBM and Compaq for use on servers.

There are two versions of this bus: PCI-X 1.0, with two speed options, PCI-X 66 (532 MB/s) and PCI-X 133 (1 GB/s); and the new PCI-X 2.0, with four speed options, PCI-X 66, PCI-X 133, PCI-X 266 (2 GB/s) and PCI-X 533 (4 GB/s). These two new speed grades are based on PCI-X133 transferring two data per clock cycle and four data per clock cycle, respectively.

PCI-X slots running at 100 MHz (800 MB/s) can be found on the market, even though they aren’t standardized by PCI-SIG (consortium that publishes PCI standard).

click to enlarge
Figure 1: Server motherboard with PCI-X slots.