OCC has published a review on the Gigabyte GA-P55-UD6

The Smart Quick Boost utility delivered a 3.84GHz clock speed with the click of the icon or just over 900MHz worth of increase, just by choosing the Twin Turbo option. The Turbo and Faster options delivered clock speed increases, but, as you can imagine, they were not as dramatic as the Twin Turbo option. The 3.84GHz clock speed is about 100Mhz higher than the utilities on the Maximus III Formula and MSI P55-GD65 delivered (at 3.7GHz), but the OC Genie is still by far the easiest to use option with the Gigabyte running a close second.

Gigabyte GA-P55-UD6 Review