Accelerated Graphics Port
Slot type created by Intel to connect video cards to the PC.
The AGP bus works at 66 MHz transfering 32 bits at a time. So, its transfer rate is of 264 MB/s (66 MHz x 32 bits / 8). This bus can work on x2, x4 and x8 modes, transfering 2, 4 or 8 data per clock tick, increasing the transfer rate to 528 MB/s, 1 GB/s and 2 GB/s, respectivelly.
Unfortunately it is not possible identify visually if an AGP slot is 1x, 2x, 4x or 8x. To know which is the highest supported speed of your AGP slot you will need to know the motherboard chipset and check on the chipset specs what are the supported modes. You can do that reading the motherboard manual or reading the support section at the motherboard manufacturer website.
AGP video cards can use the system RAM memory to store textures and z-buffering. The idea was to make cheaper video cards, since by using part of the system memory as video memory the board needs less memory chips. This feature is called DIME (Dynamic Memory Execution) or AGP Texturing. Even though AGP video cards have this feature available, only a few actually used it.
There is a bigger AGP slot called AGP Pro, which has more power lines, to be used by very high end video cards with high power consumption.
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Figure 1: AGP Slot.
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Figure 2: AGP Pro slot.
