PCI-X is a specification which defines an open standard for supporting PCI-X protocols at speed grades from 66 to 533. Revision 1.0b of the PCI-X specification defines PCI-X 66 and 133 that transfer data up to 133 MegaTransfers per second. The PCI-X 2.0a specification revises this to 266 and 533, offering up to 4.3GigaBytes per second of bandwidth. These specifications are released under PCI SIG's procedures.
PCI-X, or PCI extended, is an enhanced version of PCI (Peripheral Component Interconnect) computer bus. Although PCI-X is backward-compatible with traditional PCI devices and systems, this specification implements additional features and performance improvements include 3.3V signalling, increased speed grades, and adaptation to other form factors. PCI-X effectively doubles the speed and amount of data exchanged between the computer processor and peripherals. PCI-X bus was designed for and is ideally suited for server cards such as Fibre Channel, RAID, high-speed networking, and other demanding devices.