PCI Express® (abbreviated PCIe®) is a standard interface between the motherboard of a host computer system and any compatible add-in circuit card. Examples of host systems include personal computers, desktops, and rack-mount servers. Examples of add-in cards include graphics cards, sound cards, network cards, etc. PCI Express is an open standard that is maintained by the peripheral component interconnect special interest group (PCI-SIG), with offices in Beaverton, Oregon, USA. For more details on PCI-SIG and its PCI Express standard, see their website at www.pci-sig.org. PCI Express and PCIe are registered trademarks of PCI-SIG.
PCI Express is high speed and very robust. Version 1.1 of the standard (sometimes referred to as "Gen 1") supports up to 40 Gbps transmission speed between the motherboard and a PCIe circuit card that is plugged into the motherboard. That's a thousand times faster than a high-speed Internet connection! In addition, PCI Express has very low latency, defined as the time between request for data and the time data is received. Typical latency times for PCI Express are less than 1 microsecond. In comparison, latency times for Gigabit Ethernet are often in the 1 millisecond range.
PCI Express is widely available throughout the world. It is the latest in a long line of successful standards for connecting peripheral devices of all kinds to motherboards, beginning with the PC-XT bus in 1981. Since then the standard has been continually upgraded, from ISA, to EISA, to PCI, to PCI-X, and now PCI Express.