umm d most i ever oc da memory to was 900mhz, u can use 5-5-5-15, yet the memory was 5-5-5-18.. anything lower than that, u won't boot... and yea, 1.9 volts was the highest i carried it to. If you wanna go over that, just have some blues ready to buy some new ram..LOL
edit: i was talkin bout the markvision ram btw.. lolz