PCIX

PCIX, commonly written PCI-X, is a parallel computer bus standard that extends the PCI (Peripheral Component Interconnect) architecture to provide higher bandwidth for server and workstation expansion cards. It was developed under the auspices of the PCI Special Interest Group (PCI-SIG) and with industry participation led by Intel. PCI-X preserves PCI signaling and software compatibility while increasing the data width and clock speed, enabling faster data transfers without requiring changes to existing PCI software interfaces. In its original form, PCI-X offered a 64-bit data path operating at 66 MHz; later revisions introduced a 133 MHz mode, roughly doubling the theoretical bandwidth over the 66 MHz configuration. The 64-bit at 66 MHz topology yields about 0.5 GB/s per slot, while 64-bit at 133 MHz yields about 1.0 GB/s per slot.

PCI-X cards and motherboards were designed to be backward compatible with PCI. A PCI-X slot can accept standard PCI cards, which will operate at PCI speeds, and PCI-X cards can utilize the enhanced bandwidth when paired with a PCI-X capable host. The technology found substantial use in servers, storage controllers, high-end network adapters, and RAID controllers during the 2000s, where the demand for higher bandwidth justified the cost. As PCI Express (PCIe) emerged in the mid- to late-2000s, PCI-X gradually declined and is now largely obsolete for new systems, though it remains present in many older platforms.

See also: PCI, PCI-X, PCI Express, PCI-SIG.