I'm having some issues trying to get the i5-2500K CPU to overclock successfully with my Asus P8P67 LE motherboard.
First problem: There is NO setting in the BIOS to adjust the CPU voltage (vcore); the only way to manually adjust this is using Asus' tuning software called AI Suite II. When I adjust the setting to a certain voltage (in my case I set it to 1.22v with a 46x multiplier) and then I put a load on it, the voltage showing in both AI Suite II and CPU-Z was 1.38v. Why is it reading at a higher voltage than what I set it to? Is it dangerous to have that voltage gap (1.22v vs 1.38v)? I know you're not supposed to give these Sandy Bridge processors too much voltage so I didn't plan on going higher than the current setting. I'd be relatively happy with my 4.6Ghz OC if I knew it was safe.
Second problem: While stress testing with Prime95, the multiplier seems to go back and forth between 46x and 33x, almost like it's being throttled for some reason. CoreTemp reports my cores are getting as hot as 65-70C which I wouldn't think would trigger throttling and my huge Corsair A70 cooler is still cool to the touch. How can I keep the multiplier/frequency steady? It would be frustrating to be playing a game and have the frame rate keep speeding up and slowing down.
Any advice would be appreciated, because I don't want to have to return my board if I can make this work. Asus marketed that all of their P67 line boards could be used for overclocking so I'm getting frustrated on why this doesn't seem to be going well. Granted, this is my first time overclocking but I've read several guides on how it's done to educate myself.
I can provide screenshots and/or more information if that would help.
First: The problem is not your board. Returning it for another model won't solve your problem.
Second: Prime95 stresses your CPU more than any game ever will. Your gaming temps will likely be 15-20ºC less than your Prime95 temps. Your CPU won't throttle at those gaming temps.
Third: The new CPUs are designed to throttle their Turbo Boost down based on thermal load. When you overclock, you are simply turning up the Turbo Boost. Therefore, your overclock may be variable if you can't control the temps adequately enough.
Sandy Bridge overclocking is still so new than any guides not done by technical specialists may not be totally accurate. A guide like this should be what you go by.
Disabling the SpeedStep and CStates settings in the BIOS may solve your problem but they may also lead to loss of hard drive performance.
As far as voltage goes, 1.38v should be safe as long as you control the temps. In that guide I pointed you to, ASUS Technical Marketing Specialist Juan_Jose goes into the voltages and other stuff as well.
Edit: Also, check to see if there is a BIOS update for your board. It may enable some settings that could help you.