Breaking Intel's Overclock Lock: The REAL Story@ 2004/07/19
Both Abit and Asus employ similar methods to work around the Overclock lock, with varying degrees of success. Both manufacturers looked at chipset voltage, but decided it only provided limited enhancement for 925X/915 overclocking. They both provide this option in BIOS, but it is not a major part of the Overclock workaround.
At boot, both Asus and Abit manipulate the PCI Express frequency and set ratios that result in a lower PCIe frequency than would be expected at a given clock frequency. Since PCIe frequency and CPU clock frequency are derived from the same PLL, then a Clock frequency of 258 (FSB of 1032), for example, would result in a PCIe frequency of 129. In fact, the Abit PCIe clock at 258 is 118, below the maximum of 120 for most nVidia PCIe cards.