AGP PORT

AGP PORT:
                AGP Standards for: Accelerated Graphic Port.

                It is an interface specification developed by Intel . It is design specially for the throughput demands of 3D graphics in which the graphic controller can directly access main memory. It is of 32 bit wide and runs at 66MHz and has a band width of 266MBPS where as ,PCI bandwidth is 133 MBPS. Agp also has two optional faster modes with through put of 533 MBPS and 1.07 GBPS.

System Requirments of AGP:

1. The chip set must support AGP.
2. The motherboard must be equipped with an AGP bus slots.  

Features of AGP :

1. Texturing also called as direct memory execute mode which allows textures to be stored on main memory.
2. Side band addressing : It speed's up data transfer by sending command instructions in a seperate parallel channel.
3. pipelining: It enables the graphics card to send instructions to gether instead of sendind one instruction at a time.

                           As computers became increasingly graphically oriented, successive generations of graphics adapters began to push the limits of PCI, a bus with shared bandwidth. This led to the development of AGP, a "bus" dedicated to graphics adapters.

                            The primary advantage of AGP over PCI is that it provides a dedicated pathway between the slot and the processor rather than sharing the PCI bus. In addition to a lack of contention for the bus, the point-to-point connection allows for higher clock speeds. AGP also uses sideband addressing, meaning that the address and data buses are separated so the entire packet does not need to be read to get addressing information. This is done by adding eight extra 8-bit buses which allow the graphics controller to issue new AGP requests and commands at the same time with other AGP data flowing via the main 32 address/data (AD) lines. This results in improved overall AGP data throughput.

                           In addition, to load a texture, a PCI graphics card must copy it from the system's RAM into the card's framebuffer, whereas an AGP card is capable of reading textures directly from system RAM using the Graphics Address Remapping Table (GART). GART reapportions main memory as needed for texture storage, allowing the graphics card to access them directly. The maximum amount of system memory available to AGP is defined as the AGP aperture.