I just got my 2600k and I'm OCing using the turbo boost. I'm not after max performance, just a bump. I want to keep the power savings by allowing the pcu to adjust freq as needed as opposed to just pinning the cores to 4.2GHz all the time.
What I find interesting is how the chip appears to throttle back a little bit under load. Using cpuz, I can see the chip go from power-saving mode (16x) to 4.2GHz (42x) as soon as I start prime95. Temps end up stabilizing around 62C. Somewhere about 20-25 seconds in, cpuz says the freq goes down to 4GHz(40x). Can anyone fill me in as to why that is happening? It isn't temp related is it? It's only a 5% decrease so I'm not going to cry myself to sleep about it. But I'm very curious as to why this is happening. Anyone?
Also: do some folks really notice a difference in responsiveness when the cpu is saving power at 16x? The millisecond you try to do anything it ramps up to wherever you want. I've watched it go and have not noticed a blip of lag whatsoever...
The reason your CPU is throttling to a lower speed even though the temp is only mid-60s is because the CPU is drawing more wattage than your settings currently allow. It decreases speed so that it stays within the limit.
In the ONE menu of the BIOS are two settings: Power Limit 1 Value and Power Limit 2 Value. Change PL1V to 100 or so, and PL2V to 125 or so. Then save and exit. That should solve your issue.