My Opteron 165 Overclock

I've been overclocking slowly over the last few weeks and I seem to have hit a wall at 2.6GHz. Here's my overclocking log so far:

2.4 at stock volts
2.5 at 1.375 volts
2.6 at 1.4 volts

Core 0 runs perfectly stable at 2.6 with 1.36 volts but Core 1 won't run Prime95 for more than a minute. It takes 1.4 volts to get core 1 stable at 2.6. So i've tried burning it in some more to see if I can get it stable at a lower vcore but it doesn't seem to be working at all. Am I supposed to burn it in for more than 14 hours to see any noticeable improvements?

I've also tried 2.7GHz at 1.55 volts with load temps of 38°C but it wasn't completely stable. I didn't want increase the vcore any higher because I was afraid of causing damage to my cpu. Does anyone know what the highest safe vcore is for everyday use?

Tottaly dependent on temps. With a load at 38C i would say give it a little more juice. My general rule of thumb is 1.6v on air, 1.65v if you have good temps. My experience on these cpu's has been higher volts = less stability. I've found that there is a sweet spot more or less. At a certain point the cpu will generally stop responding to more volts and it actually becomes counter productive due to the increase in temps. In your case with a load temp at 38C on 1.55v i would say you're safe to test a little higher to see if it yeilds results.

Have you ruled out all other hardware as being the problem? Many times when the CPU won't go any higher, the memory/board/cooling ect ect can be at play.

I'm running at 2.7GHz at 1.4 volts as I type this and Core 1 is running stable but Core 0 fails Prime95. So I'm pretty sure its not my motherboard or ram thats causing the problem. I think its the week core thats holding me back. I'm going to try upping the vcore again and see if I can get it stable.

I tried getting Core 1 stable at 2.7GHz and I got it to run Prime95 from anywhere between 37-45 min before it gets an error. This was done at 1.525 volts and increasing it to 1.55 didn't help stabilize it. I might try burning it in for another 14-20 hours or so and see if that helps. If not I might try increasing the vcore again but it doesn't look like its worth it to run it at such a high vcore just to gain an extra 100MHz.