Wow, lots of good info in this thread, huge thanks to Cryptik and mikeyakame. Previously I would just leave vtt and gtlref on auto on my p5q pro-e8400, course that didn't get me anywhere as the auto values seem way off even at low fsb speed .

I notice I have no option for changing gtlref nb which is kind of a bummer. Guess I shouldn't have cheaped out on my mobo