Still fighting to get my 2600K 5GHz stable with HT-Off. I know my problem is not Vcore related. I've tried many combinations, including lowering CPU PLL to 1.700v (Made it more unstable). Also tried 1.7125v with no success. So now I'm trying 1.8250v to see where that brings me.
Getting a Sandybridge stable at 5GHz seems to be a hard task...
This is getting more and more interesting... I've found one FFT that causes problems. The 1344KB FFT always makes it error on one of the cores or BSOD. So now I've just consentrated in that one, and it fails fast, each time. I'm trying everything else than upping Vcore.
Update: The 1344KB FFT actually failed after equal short time even if I upped the Vcore by two notches! Very interesting!
Update2: The 1344KB FFT would not let me pass even if I upped the Vcore from 1.46v (Even though 1.46v seems to work for most other FFT's) up to 1.49v at 100 x50! I've downed multi to x49 now, and now it seems fine. So it will be very interesting when I try 102.1 x49 = 5GHz! I suspect this is somehow related to my CPU and the x50 multi.
Update 3: Quoted from the Sandy Stable Club:
Edited by turrican9 - 7/24/11 at 3:15pm
Originally Posted by turrican9
I've actually isolated one very, very difficult FFT for my system. The 1344KB FFT. It seems my CPU will pass almost any FFT at 5GHz at 1.460v Vcore, LLC Ultra high, but not this particular FFT. I've even tried all the way up to 1.49v Vcore only running 1344KB - 1344KB and 6000MB. It fails fast. I've even tried 49 x102.1 to rule out the multi.
This is also true at lower speeds, this particular FFT requires alot of Vcore. If one run the usual Preset of 15 minutes per FFT, this particular FFT should show up after about 3 hours + according to my calculations.
I'm using this particular FFT at 4.9GHz right now and so far it seems good at about 1.432v Vcore. This is using + 0.060 Offset and LLC at Ultra high. + 0.040 Offset failed fast at this FFT. HT is disabled in all these tests. If it holds at 1.432v Vcore at 4.9GHz, and my CPU will not pass this particular FFT at 5GHz even at 1.48v - 1.49v (Fails fast on 1344KB - 1344KB but can go for hours on other FFT's with 1.46v Vcore.) Vcore, my CPU is not good for 5GHz.
I would like others to try this particular FFT, to see if they also find this one much harder than any other FFT. If so, we may have a breakthrough as to do a very fast test before starting the usual preset. This will save us ALOT of time!
Select Blend Custom and type in 1344 - 1344 and type in as much RAM as you can.
Update: It is doing fine at 1.432v Vcore and 4.9GHz. It will not at 5GHz and upto 1.49v Vcore. I've even tried about 4.995MHz, failed there also. So it seems I have some kind of wall close to 5GHz, but only with the 1344 - 1344 FFT.