People have seen different "Steppings" of the T-Bird core, AXIA is one common on 1.2 and up, and I've seen a few other like AYHJA, AYHJAR. etc. I couldn't tell u which is the best, but it really only matters if u want to oc, AXIA oces very well and I've heard some big leauge oces out of AYHJAR like 1.6GHz, but that's all I know.