Intel fellow François Piednoel decided to give the Phenom II hell by showing off the overclocking potential of the Core i7. With an Intel desktop motherboard, an overvolted (cherry-picked?) Core i7 chip and watercooling he was able to hit 4610MHz:
They did it on an Intel desktop motherboard powered by Intel's desktop control center, something that lets you overclock from Windows. The voltage was all the way to 1.44V, whereas the chipset needed 1.21V.
Host frequency clock, something that we used to call FSB speed of the machine is 144MHz, which multiplied by the 32 multiplier gives you the 4610MHz number.
The CPU temperature was at 61 degree Celsius while the CPU Voltage regulator was at 31 °C and chipset at 41 °C. The clock is much higher than the one you can score on Phenom II, but Intel’s CPU used here is much more expensive.