When I was testing my OC I would watch CPU-Z like a hawk until I downloaded HWmonitor. With my 965 I've had to set my voltages to my "spike" voltage. Under load @3.8 for me It runs 1.42~1.45v 80% of the time and would peak to 1.472v about 15% of the time and spike to 1.488v the last 5%. I was able to set my voltage to us upto 1.475v but maybe once every 6hrs it would crash. I upped my voltage one more notch and then it was stable through 3x 12hr tests.
I wouldn't think that 0.003v would make you crash, but there's a chance? just try upping the voltage a little.
Edit: depending on the BIOS/ program your using to OC, there should be a way to set your voltage to use UP TO X amount instead of directly going to and staying at the selected voltage.
In my ancient BIOS I have a "CPU-Overvoltage" setting that gives me 50mv/100mv/150mv over my stock voltage of 1.4v. So I can set my voltage cap at 1.45v/1.5v/1.55v
I crash using 50mv but Im stable using 100mv and it never goes above 1.488v that it spikes to rarely.
I would look at the voltage required for each .1ghz for me its:
3.7 @1.452v on stock voltages of 1.4v
3.8 @1.488v with 100mv
3.9 @1.552v with 150mv
Sadly I can't get 4.0 stable with my setup. Edited by Sadmoto - 7/1/13 at 1:41pm