i have little unstable problem, its not PSU related, because i was lucky to test 3 diffrent PSUs with teh phenom

MIST/Cooltek 600W (12v 4x20A)
Corsair 620HX (12v 3x18A)
Hiper Type-R 580W Blue

i cant get it stable at 2.8ghz
temps are around ~55c
testing 2.1v on ram atm

any recommendations?