Accelerated Graphics Port (AGP)

The Accelerated Graphics Port (also called Advanced Graphics Port) is a high-speed point-to-point channel for attaching a single device (generally a graphics card) to a computer"s motherboard, primarily to assist in the acceleration of 3D computer graphics. Many classify AGP as a type of computer bus, but this is something of a misnomer since buses generally allow multiple devices to be connected, while AGP does not. Some motherboards have been built with multiple independent AGP slots.

AGP dynamically allocates the PC"s normal RAM to store the screen image and to support some features. RAM used in this manner is referred to as the AGP Aperture. AGP originated from Intel, and it was first built into a chipset for the Pentium II microprocessor in 1997. AGP cards generally slightly exceed PCI cards in length and can be recognized by a typical "hook" at the inner end of the connector, which does not exist on PCI cards.

AGP versions includes:

In addition, AGP Pro cards of various types exist. They require more power and are often longer than standard AGP card (though they only connect to one AGP slot). These cards are usually used to accelerate the professional computer-aided design applications employed in the fields of architecture, machining, engineering, and similar fields.

The AGP bus is 32 bits wide, just the same as PCI is, but instead of running at half of the system (memory) bus speed the way PCI does, it runs at full bus speed. This means that on a standard Pentium II motherboard AGP runs at 66 MHz instead of the PCI bus"s 33 MHz. This of course immediately doubles the bandwidth of the port; instead of the limit of 127.2 MB/s as with PCI, AGP in its lowest speed mode has a bandwidth of 254.3 MB/s. The AGP specification is in fact based on the PCI 2.1 specification, which includes a high-bandwidth 66 MHz speed that was never implemented on the PC.

This reserved pin should be connected to Ground