OCC has published a review on the Gigabyte GA-P55A-UD6 and GA-P55A-UD4P

For some reason these newer chips like odd numbered multipliers, so I decided to stick with a multiplier of 21 rather then staying with the beloved 20. I began by increasing the FSB in increments of 10, and then increasing the voltage when needed. I also tried to run my memory as close to 1600MHz as I could. For this reason I would occasionally have to adjust the memory multiplier, which was extremely easy to do. I was surprised because, on every other 1156 board I've used, I've only been able to get my i5 to around 4.1Ghz. With the UD4P, I was able to push slightly above 4.3GHz. Not to shabby! I'm sure with a bit more tweaking one could do some serious damage with this board.

Gigabyte GA-P55A-UD6 and GA-P55A-UD4P Review