Even with a new BIOS for our Asus P6TD Deluxe motherboard, with the vcore boosted to 1.45V, the QPI raised to 204MHz and Turbo Boost disabled, we were only able to overclock the i7-920 from 2.66GHz to 4.08GHz. This is still a great overclock, and increased performance magnificently with all the benchmark results improving accordingly.
In contrast, the i7-930, using exactly the same voltages, but with a CPU multiplier of 21x and QPI of 205MHz, was happy to run for hours on end at 4.3GHz. This is quite frankly a fantastic overclock for a standard LGA1366 Core i7, and more in the realm of what you'd expect from a far more expensive Extreme Edition. At 4.3GHz, the i7-930 returned markably better benchmark results than the overclocked i7-920.