it's the mobo limit u, not ur proc well i'm on abit NV8, doin 340htt x7 now with 1.4v only, some other people on the xtremeforum is doin 400htt, i'm totally crazy when i read tht so far the best 6100 chipset mobo is biostar, it can be OC to 347htt primestable as far as i've seen, maybe he's on a 3rd party graphic card but i hv no idea for tht prathapml, try to lower down ur htt multiplier and use ram divider, all sempron E6 can do 300htt minimum