Overclocking Is Limited By The CPU!, Continued
However, the main memory was not able to cope with the high FSB clock when operated at a ratio of 3:4 (DDR2-533 when running FSB800). For this reason, we had to reduce the ratio to 1:1 at 260 MHz FSB and above (FSB1066 mode selected in the BIOS). The resulting memory clock speed of course dropped considerably, but this was necessary to allow us to choose even higher FSB speeds.
Unfortunately, we did not have access to a P4 processor that would allow us to select multipliers smaller than 14. Despite this, we decided to cool down the CPU using a self-made Socket 775 processor kit for the VapoChill LS compressor cooler, and were able to hit slightly more than 300 MHz FSB clock for a few minutes. This makes it pretty clear that Abit's AA8XE Fatal1ty board would very likely be able to hit new FSB records, if processors were able to support faster overclocked FSB speeds by offering smaller multipliers.
We were able to hit 280+ MHz FSB clock speeds with our P4 Processor 560. The speed was limited by the resulting CPU core clock, which would not exceed 4 GHz with regular air cooling solutions.