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).
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Figure 1: Server motherboard with PCI-X slots.