OCC has published a new review on the Asus P5Q Deluxe

Overclocking on the P5Q Deluxe could not have been easier. Leave all of the voltages alone except for the CPU Vcore and the voltage for the memory, and you can go quite far. In fact, I went right to the limits of my CPU - and beyond. The P5Q allowed me to boot the computer through 500FSB and on into MemTest 2.0, where, sadly, it could not make a complete pass. But by dropping 5 FSB, I was able to get into Windows at 495x8 with my Q9450, but stability was nowhere to be found with the Q9450 at this level - voltages, GTL ref settings, VTT, PLL, nothing seemed to help. Dropping the FSB to 480 was benchmark stable, but not much else. At this point, all of the voltages were tweaked as well as the GTL reference voltages. These allowed me to finally gain stability at 474FSB. While only 4 FSB faster than the previous best on this CPU, it's still faster. Stability means different things to different people some are fine with SuperPi stable, but in the non-benchmark record setting world, 24 hour stability is a must. Seeing how the P5Q responded without all the massive voltages needed on previous chipsets told me there is some honest potential for overclocking on the P5Q Deluxe.

Asus P5Q Deluxe Review