Odd 2600k overclock problem

[coffaholic]

Brief explanation: running 4ghz @ 1.2v on a 2600k with a Maximus Gene-z (pcie 2.0) and 16gb vengeance @1600mhz. Everything runs great. Folding, prime95, IBT, etc. It's 100% stable as far as all my testing has shown. As soon as I try to bump it to 4.1,only 4 cores will load up (in task manager) with IBT or the folding client while prime95 will load all 8. Have run the voltage up to 1.45 while at 4.1ghz and the result stayed the same, only 4 cores loaded. Tried to see how far I could get prime stable while loading all 8 cores and I am prime stable @ 4.9ghz @ 1.45v for 12hrs while looping 3dm11.


It's sat at 4ghz for a while because of cooling limitations (I was underwhelmed with the performance of the H70) but since I just installed a custom water loop, I figured I would see how far I could push this chip. I've always used prime95 as a long term stability program so I started my usual routine of upping the multi till prime95 would crash, then up the volts till it ran. I finally peaked at 4.9ghz @ 1.45v as the temps were just about touching 70c. At this point I let it run, started 3dm11 in a loop to test the whole system, and went to bed. By the time I got back to the pc, it was still going after 12hrs. I thought all was well and fired up my folding client, only to notice that it only loaded 4 of my 8 cores. I started looking for other tests besides prime95 so I ran IBT, and it only loaded 4 too, then cinebench only loaded 4. I also tried upping VCCSA/IO, CPU PLL, and PCH voltages up a bit to see if that would help, it did not so I reverted them to manually set stock values. I need to brush up on my BIOS skills as its been a while since I've tinkered.

So I reset my clock back to 4ghz and everything was good in the world again.

Then I tried 4.1,ran IBT right away... 4 cores This was consistent all the way to 4.9, nothing over 4ghz regardless of vcore (up to 1.45v) will load all 8 cores outside of prime95.

I have no idea what is going on but I have all weekend to try to figure it out.

Has anyone seen something like this before? Maybe some ideas on what direction to go? Other relevant information needed?

Thanks in advance

edit: OS is Win7 64bit

 

[coffaholic]

Hmm, so I tried turning off the power saving modes in the bios (c1e, speedstep, c3 & c6) and am now loading all 8 cores at 4.9ghz. Will play around more with other benchmarks too and post back later

 

[clownshoes]

Hmm, so I tried turning off the power saving modes in the bios (c1e, speedstep, c3 & c6) and am now loading all 8 cores at 4.9ghz. Will play around more with other benchmarks too and post back later

Yep, there is probably a setting in your bios that is causing this. Usually the chip will run at max speed (say 3.8 Ghz) when only 1 or 2 cores are being utilized and if all cores are stressed it may down clock to 3.5Ghz. Also, that chip only has 4 cores (8 threads when hyperthreading is enabled). If hyperthreading is disabled and it shows 4 cores being utilized 100%, your processor is still being 100% utilized. It's unlikely it has anything to do with the voltage. If your chip isn't getting enough voltage your computer will usually just blue screen.

 

[coffaholic]

Well I've been playing games most of the afternoon and everything is running great. Got about an hour of IBT + 3dm11 in and all was well there too. My idle power draw is a bit higher now without the power saving options on but since I fold, my machine is never idle anyways.

HT was always on too.