The graphics card must communicate with the CPU by connecting to the motherboard. This is by way of a computer (bus) connector. In modern graphics cards, the interface is either though PCI (Peripheral Component Interconnect) or AGP (Accelerated Graphics Port). AGP has a much faster transfer rate than PCI and normally mid- to high-end cards are AGP compatible. PCI is still used today in lower end cards, and was a major improvement over the old connections. Not every PC has a dedicated graphics card though (See Graphics Card Alternatives). Before the advent of PCI, most graphics cards connected through ISA (industry Standard Architecture).

High-end graphics cards, such as this ATi RADEON 9700 Pro connect to the motherboard through AGP.

Specifications

AGP - The fastest AGP today, 8x, operates @ 533 MHz with a transfer rate of 2.133 GBps. To see a diagram of how AGP works with the processor and other PC components, click here.

PCI - The fastest PCI buses have a bus width of 64 bits which operate @ 133 MHz and a transfer rate of 1 GBps. To see a diagram of how PCI works with the processor and other PC components, click here.