Writing Device Drivers

PCI Express

The standard PCI bus has evolved into PCI Express. PCI Express is the next generation high performance I/O bus for connecting peripheral devices in such applications as desktop, mobile, workstation, server, embedded computing and communication platforms.

PCI Express improves bus performance, reduces overall system cost and takes advantage of new developments in computer design. PCI Express uses a serial, point-to-point type interconnect for communication between two devices. Using switches enables users to connect a large number of devices together in a system. Serial interconnect implies fewer pins per device package, which reduces cost and makes the performance highly scalable.

The PCI Express bus has built-in features to accommodate the following technologies:

A PCI Express interconnect that connects two devices together is called a link. A link can either be x1, x2, x4, x8, x12, x16 or x32 bidirectional signal pairs. These signals are called lanes. The bandwidth (x1) of each lane is 500 MB/sec in duplex mode. Although PCI-X and PCI Express have different hardware connections, the two buses are identical from a driver writer's point of view. PCI-X is a shared bus. For example, all the devices on the bus share a single set of data lines and signal lines. PCI-Express is a switched bus, which enables more efficient use of the bandwidth between the devices and the system bus.

For more information on PCI Express, please refer to the following web site: http://www.pcisig.com/home