For 4 ghz I think it needs around 1.45-1.475v, but you should overclock step by step not going from 3.4 to 4ghz instant, go like 3.6, 3.8 then 4 ghz. Also when you have overclocked to 4ghz there is other stuff to make it stable, its not just cpu speed. I will tell my settings for 3.8ghz
First you need
CPU load line calibration set to Extreme (if you have a asus board) - This will help in cpu loads, sometimmes voltage will throttle down and make you crash.
CPU Power phase control to Extreme - This settings makes your cpu use more power which helps alot in overclocking, there is 3 type, Standard, Optimized (this setting is best for saving electricity and performace at the same time), and extreme is full power.
CPU Power duty to Extreme - This settings also helps with overclocking and gives you full phase power all the time, the other one dont remember calcuate the power from heat inside ur pc so 1 spot doesnt get overheated etc, in the long turn this setting will get useless so just go extreme.
CPU spread spectrum DISABLED - Its super important to make this setting to disabled it will help to overclock alot, everyone who overclocks always disables this.
This is pretty much I hope ur overclock goes well.
The signs of bad overlock is just BSOD and heat, so try to balance with the settings, voltages and heat.
You cant just crank up multipler and voltages , you have to give the right powers and stuff before doing that, and that will make you give higher overlocks on lower settings, like me, I got 3.8gz at 1.368v thats amazing.
then it comes CPU/NB speed oh man this is the godmode stock is 2000mhz, When you overclock your cpu/nb speed, you have to overclock always the CPU/NB aswell or u will kinda bottleneck the cpu and ram. If lets say you have a 1600mhz RAM that ram is 800mhz right? so (800*2) = 1600mhz and NB shoudl always be 3 times faster then ur ram, but it can always be higher of course so 800*3 = 2400 NB. that will give you overral performance boost between cpu and memory controller without overclocking FSB and RAM! yeahh
But remember the max ram for 965 is 1333 so you dont need 1600mhz, just go with CPU/NB 2400-2600 and increase the CPU/NB voltage between 1.2 - 1.3, dont ever go above 1.35v.
I got mine at 3.8 ghz/1.368v and 2600 NB/1.25v the performance is amazing, you will notice higher performance at memory WEI (windows index) when you re-run the test. Mine went from 7.5 to 7.7 just from going 2000mhz to 2600mhz on CPU/NB.
Edited by Denebz - 11/7/12 at 7:26pm