PCI Speed and Overclocking: A Closer Look at A64 and P4 Chipsetsby Wesley Fink on February 16, 2004 9:42 AM EST
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PCI Speed and Overclocking: How We TestedAt stocks speeds and a x1 setting on the Geiger, the PCI bus is reported as 33.3MHz:
The shot above was actually taken on an Asus P4C800-E running at a 250 (1000FSB) setting. When PCI lock is working, the PCI bus stays around the default of 33.3. AGP speed is a 2X multiple of PCI in the most common setup.
When the PCI bus floats, or is unlocked, the PCI speed floats with FSB settings. You can see this here where the base FSB is set at 210:
The PCI is 1/6 the base setting of 210, or 35. This level of overclock is generally not a problem even when the PCI bus floats.
Raising the base FSB to 220, PCI increases to 36.6, or an unlocked AGP of 73.
This is often a problem for current AGP cards. Our ATI Radeon 9800 PRO tests cards generally fail in intensive benchmarking above an unlocked base setting of around 218-220.