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New Overclocker, need help with stress testing problems!!

Hey guys, so I just built myself a new pc and I'm finally getting around to overclocking it. I have an Intel Core i7 4790k, Gigabyte gtx 970 g1 gaming, Asus Maximus VII Hero (z97), g.skill trident x 2400mhz cas 10 ram (I know the ram is kind of a waste, but there was a sale and I couldnt resist :D), and a Corsair h100i. Anyways, I got to 4.7 ghz with 1.225 vcore (I had gone up to 2.8, I'll explain further in the post), and got it stable with 30 passes of Intel Burn Test on very high (I don't have the memory for maximum mode), and got it somewhat stable in aida64's free demo at a few hours. However, that was only after 5 hours of struggling with prime95. I just can't get it stable in prime no matter what, even up to 2.8 vcore, which had my temps up to 92 degrees Celsius in Intel Burn Test, but it still wasn't stable in prime. I am using realtemp for my temps. I either get BSOD or an error message from prime which boots me back to the desktop (windows 8.1 pro btw). Also, I'm running my memory at its rated xmp profile of 2400mhz, which I know holds the CPU back, and yes, I know that core is king, but its an OCD thing, so my ram is stuck at 2400 :). I thought IBT was supposed to be better than prime, and yet prime refuses to work? Could it be an installation error of prime? In case it matters, my GPU is overclocked to a +115 with a +330 for memory clock speed in msi afterburner (I don't have the exact numbers since I don't have access to my pc right now). Any help would be appreciated.
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  1. Which test are you running with Prime95? The FFT test doesn't work very well with Haswell CPU's despite using the same instructions as the blend test... which does work well lol.
  2. Best answer
    anti-duck said:
    Which test are you running with Prime95? The FFT test doesn't work very well with Haswell CPU's despite using the same instructions as the blend test... which does work well lol.


    Not quite accurate.

    Core i 2nd, 3rd and 4th Generation CPU's have AVX (Advanced Vector Extension) instruction sets. Recent versions of Prime95 (28.5) run AVX code on the Floating Point Unit (FPU) math coprocessor, which produces unrealistically high temperatures. The FPU test in the software utility AIDA64 shows the same results.

    Prime95 v26.6 produces temperatures on 3rd and 4th Generation processors more consistent with 2nd Generation, which also have AVX instructions, but do not suffer from thermal extremes due to having a soldered Integrated Heat Spreader and a 35% larger Die.

    Please download Prime95 version 26.6 - http://windows-downloads-center.blogspot.com/2011/04/prime95-266.html

    Run Small FFT's ... your core temperatures will test 10 to 20C cooler.

    Also, please read this Tom's Sticky: Intel Temperature Guide - http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html

    CT :sol:
  3. anti-duck said:
    Which test are you running with Prime95? The FFT test doesn't work very well with Haswell CPU's despite using the same instructions as the blend test... which does work well lol.


    Yea, I'm running blend on version 28.something (I think 6 or something-ish?).

    CompuTronix said:
    anti-duck said:
    Which test are you running with Prime95? The FFT test doesn't work very well with Haswell CPU's despite using the same instructions as the blend test... which does work well lol.


    Not quite accurate.

    Core i 2nd, 3rd and 4th Generation CPU's have AVX (Advanced Vector Extension) instruction sets. Recent versions of Prime95 (28.5) run AVX code on the Floating Point Unit (FPU) math coprocessor, which produces unrealistically high temperatures. The FPU test in the software utility AIDA64 shows the same results.

    Prime95 v26.6 produces temperatures on 3rd and 4th Generation processors more consistent with 2nd Generation, which also have AVX instructions, but do not suffer from thermal extremes due to having a soldered Integrated Heat Spreader and a 35% larger Die.

    Please download Prime95 version 26.6 - http://windows-downloads-center.blogspot.com/2011/04/prime95-266.html

    Run Small FFT's ... your core temperatures will test 10 to 20C cooler.

    Also, please read this Tom's Sticky: Intel Temperature Guide - http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html

    CT :sol:


    Very interesting read. I'll be sure to download version 26.6 in the morning. So I'm assuming that means that my system is stable even though the latest version of prime keeps crashing? Also, I'm running on 1.225 volts, but looking at the calculation that a 100mhz increase in core equates to a .040 - .050 core increase, do I need to up the core? My temps on aida64 are in the high 60s, mid 70's, but intel burn test raises it really really high. I'm aware that linpack is ridiculously hot, but would a voltage jump increase stability, even though I'm on an CLC? Anyways, thanks for the help guys, this will hopefully let me keep my 4.7ghz goal a reality!
  4. You assume fairly correctly.

    " ... Prime95 Small FFT's is the standard for CPU thermal testing, because it's a steady-state 100% workload.

    Prime95's default test, Blend, is a cyclic workload for testing memory stability, and Large FFT's combines CPU and memory tests. As such, Blend and Large FFT's both have cyclic workloads which are unsuitable for CPU thermal testing.

    Other stability tests such as Linpack and Intel Burn Test have cycles that load all registers with all one's, which is equivalent to a 110% workload, and are also unsuitable for CPU thermal testing. The software utility OCCT runs elements of Linpack and Prime95.

    http://i1275.photobucket.com/albums/y446/CompuTronix52/SpeedFanTempGuideGraph_zpsd98effba.jpgShown above from left to right: Small FFT's, Blend, Linpack and Intel Burn Test.

    Note the steady-state thermal signatures of Small FFT's, which allows accurate measurements of Core temperatures.

    http://i1275.photobucket.com/albums/y446/CompuTronix52/SmallFFTsIntelETUAIDA64_zps2b0c9ff0.jpgShown above from left to right: Small FFT's, Intel Extreme Tuning Utility CPU Test, and AIDA64 CPU Test.

    The "Charts" in SpeedFan span 13 minutes, and show how each test creates different thermal signatures. Intel Extreme Tuning Utility is also a cyclic workload. Although AIDA64's CPU test is steady-state, the workload is insufficient ... "

    CT :sol:
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