Hello,On asus qualified vendor list for P7P55D-E PRO which is a dual channel board, they qualify 3 stick kits for "A"-"B"-"C" configuration. Where does the third stick go??
You can use two of the sticks in dual-channel mode or three sticks in single-channel mode. I'd go dual-channel. I have a ton of triple-channel kits where one module died, that I'm using in dual-channel motherboards.