PCI Express (PCIe) is a scalable I/O serial bus technology that has replaced previous PCI slots on motherboards. It allows for hot swapping, uses less power, and is scalable. PCIe comes in x1, x2, and x16 formats, with the latter replacing AGP for graphics cards. PCIe should not be confused with PCI-X, which is used in the server market. Intel first introduced PCI technology in the early 1990s to replace ISA.
Peripheral Component Interconnect (PCI) Express (PCIe) is a scalable Input/Output (I/O) serial bus technology that has largely replaced the previous PCI slots on motherboards. It is a port that allows certain internal components to be installed in a computer. In 2004, PCI Express slots began appearing alongside standard slots, initiating a gradual transition to the new technology. While some standard PCI slots can still be found on motherboards, many computer users prefer PCI express for graphics cards and other components.
The purpose of PCI Express
PCIe slots are found on many motherboards, allowing computer users to install components into them. They allow the motherboard and other software in a computer to access and use devices plugged into these slots. While PCIe was used throughout the first decade of the 21st century, new slots are likely to replace them in the future.
Benefits of PCIe technology
PCI Express is a point-to-point connection, which means it doesn’t share bandwidth but communicates directly with devices via a switch that directs the flow of data. This allows for “hot swapping” or “hot plugging,” which means that cards in PCIe slots can be swapped out without turning off the computer, and they use less power than older PCI technology. One of the most promising features of PCIe is that it is scalable, meaning that more bandwidth can be achieved by adding more “lanes”.
PCI Express has several additional benefits, not only for the user but also for manufacturers. It can be implemented as a unifying I/O fabric for desktops, servers and workstations and is cheaper than standard PCI to implement at the motherboard level. This keeps costs down for the consumer. It is also designed to be backward compatible with older operating systems and PCI device drivers.
Types of PCIe formats
The initial launch of PCI Express provided three options for consumers: x1, x2, and x16. These numbers represent “lanes:” x1 has 1 lane; x2 has 2 lanes and x16 has 16. Each lane is bi-directional and consists of 4 pins. The lanes in version 1.x of PCIe had a lower delivery transfer rate, but PCIe 3.0 introduced a transfer rate of 500 megabytes per second (MBps) in each direction for a total of 1,000 MBps or 1 gigabyte per second ( GBps), per lane.
PCIe
Lanes
Play
MBps
Scope
x1
1
4
1 GBps
Device
x2
2
8
2 GBps
Device
x16
16
64
16 GBps
Graphic card
PCIe and graphics cards
The 16-lane (x16) slot replaced the Accelerated Graphics Port (AGP) on many motherboards and fits a PCIe graphics card. Cards that include x1 and x2 slots usually have them for other components, such as sound or network cards. As computer graphics demands increase, x32 and x64 slots may become available, and future versions of PCIe may improve data speeds in the lane.
Other PCI technologies
PCI Express should not be confused with PCI eXtended (PCI-X), which is used in the server market. PCI-X enhanced over the standard PCI bus to provide a maximum bandwidth of 1GBps. PCIe was also developed for the server market, initially with the x4, x8 and x12 formats reserved. This far exceeds PCI-X capability.
History of PCI technology
Intel first introduced PCI technology in the early 1990s to replace the Industry Standard Architecture (ISA) bus. While robust enough to last over a decade, the total available bandwidth of just 133 MBps, shared between slots, meant high-demand devices quickly overwhelmed computer resources. In 1997 this problem was partially alleviated by the implementation of a separate AGP slot with dedicated bandwidth. However, as component manufacturers developed many high-demand devices for computers, a new architecture was needed, which resulted in the introduction of PCI Express.
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