What Are PCI and PCI-Express
When it comes to purchasing motherboards or add-in cards such as internal television cards, controller cards, graphics cards or sound cards for your computer, you'll often hear the terms "PCI" and "PCI-Express." These are interfaces, also known as hardware busses, which are used for connecting various devices such as those mentioned above. PCI stands for "Peripheral Component Interconnect." Designed by Intel and introduced in 1993, the standard PCI interface is still in use, although it is slowly being phased out in favour of PCI-Express standards. Most motherboards still provide PCI slots for older hardware, however. PCI itself replaced the older ISA (Industry Standard Architecture) back in the 90s.
Most of today's add-in cards require a PCI-Express socket. Modern motherboards are normally equipped with all of the required PCI-Express sockets enabling you to install various add-in cards. PCI-Express sockets come in various different sizes, each size being of a different speed and designed for different types of hardware. For example, today's graphics cards use the PCI-Express x16 slot while most other add-in cards such as sound cards and controller cards providing extra USB ports and other connectivity options use the PCI-Express x1 slot. This is also the physically smallest slot. Many motherboards are also equipped with a PCI-Express x4 slot.
More expensive motherboards often provide two PCI-Express x16 slots, allowing you to install two graphics cards. This can greatly improve the performance of 3D video games and productivity applications. Graphics cards previously used the AGP (Accelerated Graphics Port) slot, although these are now extremely rare and have been phased out from newer computers and components.
PCI and PCI-Express come in various different forms. Servers, for example, are usually equipped with extended PCI slots known as PCI-X slots, although these are of no concern to the average home user. Laptop computers are equipped with MiniPCI slots, although the upgrade possibilities are limited as far as the average user is concerned. Laptops with dedicated graphics cards also use the PCI-Express interface, albeit in a slightly different form.