AGP aperture size
The AGP aperture size is an available option configurable through the computer CMOS setup that is usually set to a default size of 64 MB. AGP aperture size defines how much system memory (not memory on your video card) the AGP controller uses for texture maps.
While it may be possible to increase the overall video performance by increasing the AGP aperture size value, we recommend leaving it at the default size. Increasing the default size only allocates more of your system memory, which is not used unless the program or game is capable of using it. Also, because more system memory is allocated, you may see an overall reduction in computer system performance.