u r so lucky use Vnb 1.2v. mine VnB is 1.26v while running 4Ghz.

@Bro Nidzamputra
i just undervolt Vcore to 1.34375v like hilmiangah said, it works..will do another lower voltage this night to test.

@clawhammer
why mine after some hours when restart running on 4.2Ghz fail. i mean the fail is appears of black screen and got sounds of Bippp... bip bip bip and after 3 sec bippp....then, what i do is reallocate the ram placement.. sometimes i need to take out my 1 stick of 2GB ram to run 4.2GHz..
what wrong? i done past prime test with 4.2Ghz last night.

my ram 2 sticks of 1GB 800mhz and 1 stick of 2GB 800mhz..

Vcore 1.34375v
vdimm 1.92v
1:1

i only running "Blend" test . is it enough only use "Blend" test alone (after running OCCT every increment)? sorry i m new on this thingy.
still on learning..

i m running 5-5-5-15 at vDimm 1.92v. i think will increase about 0.06v. any idea? 9x 450 = 4050MHz
to pass 4.2Ghz is difficult to me. 4.1Ghz mostly the same setting applied from 4GHz setting. only FSB need to change. (460x9 = 4140MHz)
i wonder my ram is the barrier gate to me or myself lack of skills?

C2D also reach 80c++? i cant believe that. (problem with case air ventilation?)

if quad proc full stress reach 80c+ is acceptable.