The Accelerated Graphics Port (AGP) is a standard outlining a high-speed, dedicated port primarily to assist in the acceleration of 3D computer graphics.
AGP operates at 66 MHz, doubled to 133 MHz, compared with PCI's 33 Mhz. AGP allows for efficient use of frame buffer memory, thereby helping 2D graphics performance as well. In fact, many RAID systems for "headless" (that is, lacking an attached display) servers plug into the empty AGP slot to take advantage of its increased throughput vs. PCI.
AGP provides a coherent memory management design which allows scattered data in system memory to be read in rapid bursts. AGP reduces the overall cost of creating high-end graphics subsystems by using existing system memory.
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