I can't find that in the UEFI, im retarded and tired after a long day
I'll give you instructions but only the changes required after applying my 3 steps OC guide. This mean I won't touch some settings that those who manually OC would actually look at.
1st mandatory step it set VCore Phase Control to Optimized under Digi+ VRM/POWER Control. This will unlock the Offset Mode option for CPU Voltage but before going back to select that option immediatly, change the VCore Load-line Calibration to 50%.
Now go back to main and select Offset Mode for CPU Voltage.
Offset Mode Sign to -
CPU Offset Voltage to 0.010
That's it. This works flawless for my Core i5-2500K @ 4.6GHz OC using the CPU Level Up option set to 4.6 (which take care of other settings). At idle using CPU-Z I read 0.992v and 1.336v full load.
I was able to run IBT at 'Higher' 5 pass without problem. As I'm writing this I'm running FurMark and IBT just for the fun of it.
Results may be different for you or anyone!