Has anyone going for high FSB experienced a hard wall? I've gone up to 563FSB without really touching anything and then I can't go any further regardless what I do. Is it common to hit such a wall then have to go crazy on the voltage to go any higher? If I go to 564FSB (or above) with the same settings, the system won't even post. Settings using a E8600:

vcore:1.43v
vpll: 1.55v
vnb: 1.40v
vtt: 1.38v
GTL: 61x 61x 58x
FSB Vref: Auto