Sorry about the quad post. Sometimes Firefox steps on its own feet.
You want to OC the P55M-UD2? I have since lost my settings, but the first thing I did was to hit the big red button in ET6. I had tried doing it the old-fashioned way, and I wanted to see what automation could do.
The big red button advertised 4200MHz, gave me 3800MHz with a BCLK of 200 or so. I set the memory timings rather loosely, set the CPU to 1.4V and the RAM voltage to 1.66V - it gives a 1.648V result, which is perfect. Intel gives a top end of 1.65V for the CPU's memory manager, and GSkill gives a top end of 1.65V for the RAM. So I tried 4000MHz. OK. Then 4200MHz. OK. No sweat. But with a 92mm heatsink I didn't want to push it.
Re-reading the comments under the review, Gary says the board held up under a full load. He does recommend not to overvolt the thing, suggests a top end of 1.45V for the CPU. Since Intel says the chip is designed to handle up to 1.4V, I will not go beyond that.
It seems that if my new Megahalems can hold down the CPU temp, routine OC'ing will be OK. Nice to know.