"400 x 10 at 1.325 volts for a first boot was a promising start to my overclocking adventure with the QX9770. 400 x 11 at 1.50 volts came easy as well but the required voltage was more than my poor water cooling setup could handle under load. At this level the stability was not there on the test system. It was stable enough to run Super Pi 1m and I was graced with the best score I have had to date. At that point I started hunting for a combination of FSB and multiplier that was acceptable for day to day use. 475 x 9 (4.3GHz) at 1.4625 volts ended up being the sweet spot for benchmarking and successfully completed our entire benchmark suite. For day to day operations, I settled on 455 x 9 (4.1GHz) at 1.395 volts. Hitting 4.0+GHz stable for everyday use makes for one e-ticket rig. Getting to the 475 FSB threshold required adjusting the northbridge voltage, FSB termination voltage, PLL volts, memory and southbridge voltages to gain stability. Getting to 4.0GHz on a Core 2 Extreme is the simple part. Getting more requires some work to make it happen. Keep the CPU temperature in check and the sky may be the limit. Of course your mileage may vary."
FULL STORY @ OVERCLOCKERSCLUB (http://www.overclockersclub.com/reviews/intel_qx9770/)