Overclocking i7 8700K, can't tell if my overclock is unstable?

Oct 28, 2018
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Hey everybody, I built my PC in March. I decided I wanted to overclock today, after it has been running smoothly for all these months.

Specs:

  • i7 8700k
    GTX 1080 Founders Edition
    MSI Z370 Gaming Pro Carbon
    G.Skill 3000mhz RGB RAM
    NZXT S340 Elite
    Corsair H115i Pro AIO
    2TB HDD / 500GB SSD
Today, I messed around with an overclock. I changed the CPU to 47 (so 4.7GHZ) and it ran pretty nice. I benchmarked and it was pretty stable. Then I upped it to 50 (so 5.0GHZ). I had my voltage at 1.35 at first, but that was getting very hot (90C'+ with AIDA64 Extreme Stress Test). So now, my current overclock is 5.0GHZ with a 1.33 voltage. Any lower and I got BSODS.

Anyways, I used AIDA64 to stress test it, and after 15 minutes it only had 1% thermal throttling. It hit like 96C though I think.

I tried using Prime95 to stress test it tonight and when I use the Small FFTS option, the test does not even work:
Code:
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Worker starting
[Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Worker starting
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Beginning a continuous self-test on your computer.
[Work thread Oct 28 01:50] Please read stress.txt.  Choose Test/Stop to end this test.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] Test 1, 1800000 Lucas-Lehmer iterations of M250519 using FMA3 FFT length 12K, Pass1=256, Pass2=48, clm=1.
[Work thread Oct 28 01:50] FATAL ERROR: Rounding was 2639862.29, expected less than 0.4
[Work thread Oct 28 01:50] Hardware failure detected, consult stress.txt file.
[Work thread Oct 28 01:50] Torture Test completed 0 tests in 0 minutes - 1 errors, 0 warnings.
[Work thread Oct 28 01:50] Worker stopped.
[Work thread Oct 28 01:50] FATAL ERROR: Rounding was 0.5, expected less than 0.4
[Work thread Oct 28 01:50] Hardware failure detected, consult stress.txt file.
[Work thread Oct 28 01:50] Torture Test completed 0 tests in 0 minutes - 1 errors, 0 warnings.
[Work thread Oct 28 01:50] FATAL ERROR: Rounding was 0.5, expected less than 0.4
[Work thread Oct 28 01:50] Worker stopped.
[Work thread Oct 28 01:50] Hardware failure detected, consult stress.txt file.
[Work thread Oct 28 01:50] FATAL ERROR: Rounding was 0.5, expected less than 0.4
[Work thread Oct 28 01:50] Hardware failure detected, consult stress.txt file.
[Work thread Oct 28 01:50] Torture Test completed 0 tests in 0 minutes - 1 errors, 0 warnings.
[Work thread Oct 28 01:50] Torture Test completed 0 tests in 0 minutes - 1 errors, 0 warnings.
[Work thread Oct 28 01:50] Worker stopped.
[Work thread Oct 28 01:50] Worker stopped.
[Work thread Oct 28 01:50] FATAL ERROR: Rounding was 0.4994246285, expected less than 0.4
[Work thread Oct 28 01:50] Hardware failure detected, consult stress.txt file.
[Work thread Oct 28 01:50] Torture Test completed 0 tests in 0 minutes - 1 errors, 0 warnings.
[Work thread Oct 28 01:50] Worker stopped.
I am wondering why it is saying hardware failure instantly after beginning the test. My PC was running pretty stable. I played GTA 5 for like two hours and the CPU wouldn't go over ~70ishC'. Also, I was playing Overwatch for hours and the CPU wouldn't get very hot either. As of right now, while typing this, the CPU is 40'C and my GPU is 40'C as well.

Why is Prime95 doing this? Is my 5.0GHZ/1.33V overclock stable? I really want to get the most out of my system, so hopefully you guys can help me get a stable 5.0GHZ overclock.

P.S. When my PC was getting very hot, the AIO was having an issue where it would flash red. I am assuming that the red flashing indicates that it is too hot, so that's why I dropped my 1.35 voltage to 1.33. Also, I tried 4.9Ghz with 1.32 and it was semi-stable. My CPU just gets kind of hot when I first boot for some reason, probably the spike in CPU usage.

Please help me, thanks



UPDATE: I just ran another stress test with AIDA64. 5GHZ / 1.33 volts. Went downstairs to make a nutella sandwhich, and when I came back up after eating my PC screen was black. My liquid cooler was flashing the default rainbow color, so I guess that means my PC just completely froze? My keyboard and mouse were both frozen. They are usually fading through colors, but it was stuck in some middle sequence. Had to hold down the power button on my PC, and it completely shut off. But the lights were still on on my peripherals... I had to completely turn off my rig from the power button on the PSU, and 3 seconds later my peripherals turned off too (finally). Anyways, when I reopened AIDA64 it said that it was terminated unsuccessfully, and the maximum reported temperature was 98C (wow...). So does this mean my chip is not capable of hitting 5.0GHz? :(
 
Okay a couple of things are going on here...

One, which version of Prime95 were you using...Prime95 version 26.6 is recommended for Intel...
Second Prime95 small FFT torture test is brutal on any CPU and an overclocked non dellided 8700K will hit 90 degrees C very fast at 5GHz and above..

Overclocking can be finicky, did you use LLC to try to balance the vcore? 1.33v is not too bad for a 5GHz overclock but I think you are reaching the thermal limits of your 8700K with the small FFT test on your cooler.

What happens in terms of Temps when you do the Prime95 test on the Blend Test only?

I went through the same as you have until I delidded my 8700K and then dropped temps by near on 20 degrees C. I have settled at a 4.9GHz at 1.278v for my 24.7 overclock. If you want the max overclock, then delidding is an option that actually does make a difference.
 
Oct 28, 2018
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I was just using the latest version of Prime95, found on their official website. I will try 26.6 right now.
And I don't know, my temps would only go up to like 65'C and get stuck there, while my CPU usage remained at 100%. Prime95 was in some strange mode. I could tell it wasn't fully torturing my CPU, and it even stated that a hardware failure was detected, most likely explaining why it was in this mode.

I don't know what LLC is. And yeah, I was reaching thermal limits most likely. My CPU hit like 98'C.

I can't run the Blend Test either, because it instantly stops due to some hardware failure.

Yeah, I might delid but idk.
 
So try testing with Prime95 version 26.6 and go for the blend test first. Also AIDA64 Extreme is a good test which provides temp monitoring as well. For Aida64 Extreme just use the System Stability Test under the Tools tab.

With regards to LLC, you usually have a number of settings from 1 to 7 or in my case with a Gigabyte board it goes, Normal, High, Turbo and Extreme...I use the High setting. What LLC does is stop the vcore drooping or lowering and keeps the vcore within a tight window...Please look it up as I know my explanation is not great but it is important when overclocking for a stable vcore.

If you cant do even the blend test in Prime95 version 26.6, then drop the clocks down to 4.8GHz and start from there going back up. Start at around 1.27v for 4.8GHz...You might be able to get a lower vcore for the 4.8GHz but its a good place to start.

Here are some setting for your motherboard and the 8700K

https://www.reddit.com/r/overclocking/comments/9gv5a2/newbie_8700k_msi_z370_gaming_pro_carbon_oc_help/

https://www.anandtech.com/show/12763/msi-z370i-gaming-pro-carbon-ac-review/9

There is a lot of trial and error as every CPU is slightly different and do read up on your motherboard and CPU combo for overclocking guides and threads as there are quiet a few out there..
 
Oct 28, 2018
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Alright well, I got Prime95 26.6 like you said. I stress tested with 4.9GHz and my screen went black and crashed. I had to reset my PC manually. Then I went to 5GHz and 1.325V and I have been using my PC all day. I mean, it runs and games fine. But i'm scared to stress test since I bet it'll do the black screen thing. Rebooting my PC feels scary when that happens because even when my PC is completely off, the peripherals stay shut off. I have to turn off the switch on my PSU to finally kill it completely. Oh yeah, and I turned off the Enhanced Multi-core Turbo thing. My temps as writing this is 37C CPU and 42C GPU.
 

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