Specs: i5 3570k @ 4.2GHz Hyper 212 EVO Asus P8Z77-V 8GB Corsair Veangence RAM
Okay, so I've trying to get my overclock stable. I think 1.160-1.168v is the limit of stability for me. However when I'm running Prime95, all the cores are able for 12hrs (haven't gone longer) but one. Around the 3-4hr mark, my 2nd core always gives me an error and stops while the other cores continue. Also, the 2nd core seems to also be the hottest. It's around 65c while the other cores are around 60-62c.
I'm testing again, I've set the CCL to High (50%) and CPU phase control to Asus Optimised. I will see if it happens again.
More aboutjust core
The difference in temperatures is normal, so don't worry about that.
As for failing though, try bumping up your voltage a little and see if it works.
Relax Ram timings as well, Found that helps when OCing my x6 1100T where 1 core kept failing.