was having alot of problems running 8400 clocked, endless adjusts with gtl's, vtt, nb, when i think clocks were stable prime wise, it bluesrceen without warning. on 1/09 and 12/24 bios
found it is to do with my raid0 array. only stock running was stable enough to boot from.
installed windows on another hdd, still using 1/09 bios, was able to run auto setting to 4.8ghz with gtl disabled, adding some volts to vtt and nb for that run.
priming now @ 4.3ghz