Need help stabilizing my Core i7 875K @ 4.0Ghz

Hi all. I've been a member here for a few years but this is my very first post here.

I'm having trouble getting my Core i7 875K to pass LinX 150+ loops or Prime95 blend over night. My system would reboot itself without BSOD (not sure if it freezes just before rebooting) after 1-3 hours running LinX/Prime95. Daily use and gaming is fine (unless I set some voltage way too low). I'd like to achieve 4GHz(200x20) for everyday use with highest stability possible. It's not that I'm being too nervous about stability but I really hate to see the BSOD while I'm in the middle of anything. ;)

P.S.
20 loops of LinX passed OK.
OCCT small/medium/large Data Set overnight passed OK.
memtest using all available ram overnight passed OK.

I've tried several combination of voltage but the problem still persist. Here's my rig detail.

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i7 875K + Venomous X w/Tt 120mm fan 2500rpm
Asus P7P55D-E bios 1101
Kingston 2x2gb 2000 CL8 (runs at 2000 8-8-8-24 1T @1.65v, tried lower it to 9-9-9-27 but no luck)
eVGA GTX480 @stock speed
Thermaltake Toughpower 750w

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and here's some voltages and configs I've tried.

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bclk 200 multiplier 20 = 4GHz
vcore = fixed 1.40 (anything lower than this would case BSOD#101)
load-line calibration = enabled
IMC voltage = 1.35v (anything lower than 1.3375 would cause BSOD#124,ramped up to 1.412 but the problem still persist)
vdimm = 1.65 (didn't want to overvolt the ram)
CPU PLL voltage = 1.80 (ramped up to 1.90v but the problem still persist)
PCH = 1.05 (ramped up to 1.10v but the problem still persist)
Spread spectrum = both disabled
C1E/EIST/TM = disabled
PCIE Frequency = 100 (ramped up to 104 but the problem still persist)

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Max temp while the air-con being on is around 92c. The whether here is simply hot :mad:.

I've heard that reducing CPU PLL voltage could help in achieving higher clock but my mobo has lower limit at 1.80v :(

Here's my CPU-Z screenshot.
http://img9.imageshack.us/img9/3136/capturewoh.jpg

Thanks in advance for any suggestions.

Try with loadline calibration off and adjust voltages back up to where you were.

Failing that memory? Last time I chased a pain in the ass problem like this looks to be it turned out to be TRD subtiming too tight.

Your temps are pretty high there too, that wont be helping things. When I was testing my i3's I found that they all froze running linx when the temps hit 93-95c, no matter what speed and cooling.

PSU will be right at the limit too. Definitely wouldnt try ocing the gtx480.

If you use the PC for gaming and browsing etc then id suggest turning hyperthreading off. Most games suffer for it being enabled, plus your temps will drop and your oc will go up.

Try this:
4.0GHz,
24 multi
167 Bclk
1.38125 CPU
1.3 IMC,
1.9875 PLL
1.45 PCH

And you need to remount your cooler with dual fans and some AS5

@theix
I would first try to run the RAM with a low and save speed during OC the CPU.
This way You can concentrate to the voltages from the CPU.
After the CPU is stable You speed up the RAM.

@OS-Wiz
I would like to understand, why 1.9875 PLL and 1.45 PCH could help to make a CPU stable?
A BCLK 167 should run stable with IMC 1.21V. Can easy be tested with Prime and In-place large FFTs and a low Multi.

1.45vpch wont help anything, thats way high for anything ive ever tried. 1.120vpch is the max i have used up to 5ghz linx.

theix, why 150 passes of linx? that is a bit over kill imo. if it passes 20 call it a day. play whatever game you play or run whatever programs you use daily, if it runs fine move on.

hello theix

@OS-Wiz
Will try 167 bclk but 1.45v on PCH is too high imo.

@MikelMolto
I already did that. 1.40v on vcore and 1.3375v on IMC is minimum for 4Ghz cpu and 2000 memory regardless of the timing.

@OC Nub
Just like I said.I need to make sure that my rig wouldn't BSOD while I'm in the middle of whatsoever :yepp:

@PatRaceTin
Hello there!

P.S. Tried LinX 300 loops last night. The system froze at 286th loop. :shakes:

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Originally Posted by theix

P.S. Tried LinX 300 loops last night. The system froze at 286th loop. :shakes:

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That is absolute pure overkill. Call it stable and never put your hardware through that much abuse again :p:

Even F@H at 100% load 24/7 for weeks can't crash any of my systems that have passed LinX 20 passes with ALL memory usage.

Man run 20 Runs of linx and 20 runs of intel burn test, 286th is pure over kill.. your system will never run that much load even gaming with everything on maxed..

What about the system being froze? Is this CPU,IMC or memory issue?
I just found out that my system froze after running a memory stress test in Intel Extreme Tuning Utility 2.0 for 2 hrs and a half.

What make the problem (CPU,IMC or memory) can be find out with Prime95.
Here is the link to: Prime95 (64bit) - 25.11.

Small FFTs: check the CPU VCore.
In-place large FFTs: check the IMC and RAM Timings
Blend: check the RAM
Custom (with Run FFT´s in place): check the overall System.

To check the RAM Memtest or Memtest86 is the better choice.

Quote:

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Originally Posted by theix

What about the system being froze? Is this CPU,IMC or memory issue?
I just found out that my system froze after running a memory stress test in Intel Extreme Tuning Utility 2.0 for 2 hrs and a half.

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Do you ever use the rig? Maybe try playing a game, looks like all you do is stress test. You run anything long enough eventually you'll find something to makes it unstable. If you want a 100% guarantee on stability just go into bios and set everything up stock and save yourself some time.

If it doesnt freeze up or bsod in the things you use the pc for it is stable enough. You may have a hard time finding any answer to what it will take to get your systems stable enough to satisfy you from anyone in the forums, most people dont run 9000 passes of LinX followed by 1200 hours of blend.

Try to reduce RAM timings to 9-9-9-24.

For me when going to higher BLCK (166 to 200, CPU remain at 4GHZ) I needed to relax the timings.

Just to add I have experienced better memory speeds and 3dmark scores when using bclk of 166 over 200. Also I was able to clock my memory higher and tighter at 166.

Seems that higher bclk is not everything.