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Graphics accelerators can be very susceptible to bus overclocking, especially the older generations of AGP video cards. Based on a 66-MHz PCI bus design, AGP cards store graphical texture data in the system's main memory. This improves 3D rendering by speeding up access to more graphical information than can be stored in the video card's onboard memory. Subsequent revisions have extended the AGP standard to include an advanced data signaling technique, which transfers information at up to eight times the rate of the original specification.
The latest generation of video cards can usually sustain AGP speeds approaching 90 MHz, though earlier models often fail above 75 MHz. Lowering the effective data transfer rate can neutralize the stress of extended speeds. AGP 4x cards must often be lowered to 2x for successful operation. In addition, disabling side-band transfers and fast-write capabilities can limit the effects of bus overclocking on stability in the AGP subsystem. AGP bus configuration can usually be altered from within a system's BIOS interface, though some video cards feature onboard jumpers.
Most games and other 3D applications will see only mild performance losses from lowered transfer rates or disabled advanced AGP. The latest graphics accelerators feature 64 to128 megabytes of onboard memory, so the need to perform texturing operations in the system's main memory is reduced. Even the most advanced 3D games rarely demand more than 32 MB of graphics memory at display resolutions below 1024 x 768. Computer-aided design applications suffer the worst performance degradation, but professionals who use such software rarely resort to overclocking. They prize data integrity and system stability, and tend to obtain speed by upgrading rather than tweaking their systems.
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