[SOLVED] Stable overclock on i7 8700k now having issues

[ian.egerton]

Hi,

I have an i7 8700k running on an ASRock Z370 extreme4 MB.

I have been running a stable OC @ 4.8Ghz with an offset of -30 for a few years now without issue. I mainly max it out running ffmpeg or handbrake for video encoding.

In the last few days I've noticed that when running handbrake the PC has started to either lock up or crash.

Any ideas what could be causing this? Should I re-seat the cpu and apply new thermal paste? I'm using an Arctic Cooler i30 CO as a cooler.

 

[ian.egerton]

Power consumptions and Core temperatures are as expected, however, you have 64mv of Vcore fluctuations during P95's steady-state workload, which indicates sloppy voltage regulation.

Just to be sure, please repeat the Prime95 Small FFTs no AVX test.

Make sure that you don't start HWiNFO until after you start P95, then record the Minimum and Maximum Vcore before you stop P95. The Vcore values will reflect the fluctuations that occur only during the P95 test, which is the information we need to verify. Average Vcore isn't useful, so don't bother recording it.

Transcoding in HandBrake produces a fluctuating workload, so I would expect considerably more Vcore fluctuations than in P95, which you found to be 144mv.

We don't need to repeat HandBrake, so just run P95 once more, if you please.

I just ran it for a few minutes (making sure I reset everything in HWiNFO).

The min is 1.184V and max is 1.248V.

 

[CompuTronix]

There it is again ... 64mv.

When Vcore spikes low at the same moment that a fluctuating workload spikes high, this is when the processor is most vulnerable to BSOD.

There are 2 solutions:

• Increase Vcore to compensate for increasingly sloppy voltage regulation.
• Replace the motherboard with a make or model of tighter voltage regulation.

Just for some background perspective, on 4th generation processors, Intel used Fully Integrated Voltage Regulators (FIVR) directly in the package, so fluctuations were minimal at only 8mv, with occasional fluctuations to 16mv; 8mv = 1 bit.

Motherboards for other generations of processors before and after 4th generation have had voltage regulation from 16 to 32mv, but as sloppy as 80mv or even worse, which is completely unacceptable. 16 to 24mv is good, 32 to 40mv is mediocre, and 48mv or greater is poor.

You can repeat the test a few more times if you like with different LLC / Vcore / offset combinations, but I think you have your answer. If VRM regulation was better when your motherboard was newer, then it certainly appears to have degraded. Regardless, 64mv of Vcore fluctuation on a steady-state workload is not good.

Sorry

CT

 

[ian.egerton]

There it is again ... 64mv.

When Vcore sags or spikes low at the same moment that a fluctuating workload spikes high, this is when the processor is most vulnerable to BSOD.

There are 2 solutions:

• Increase Vcore to compensate for increasingly sloppy voltage regulation.
• Replace the motherboard with a make or model of tighter voltage regulation.

Just for some background perspective, on 4th generation processors, Intel used Fully Integrated Voltage Regulators (FIVR) directly in the package, so fluctuations were minimal at only 8mv, with occasional fluctuations to 16mv; 8mv = 1 bit.

Motherboards for other generations of processors before and after 4th generation have had voltage regulation as sloppy as 80mv or even worse, which is completely unacceptable. 16 to 24mv is good, 32 to 40mv is mediocre, and 48mv or greater is poor.

You can repeat the test a few more times if you like with different LLC / Vcore / offset combinations, but I think you have your answer. If your motherboard's VRM regulation was better when it was newer, it certainly appears to be in a degraded condition at this time. Regardless, 64mv of Vcore fluctuation on a steady-state workload is not good.

Sorry

CT

Thanks for the reply and all the help.

I'll have a play around to see if I can get it to stabilise more. I don't stress it that often so as long as it is stable for handbrake sessions that's all I need for now.

Thanks again.

 

[CompuTronix]

One other thought; check the fasteners on the back of the motherboard for the VRM heatsinks to make sure they're snug.

 

[ian.egerton]

One other thought; check the fasteners on the back of the motherboard for the VRM heatsinks to make sure they're snug.

Sorry one more question.

Do you think it would be wise to upgrade my cooling solution to something higher rated? Something like:

Dark Rock 4
Noctua NH-U14S
Noctua NH-D15

 

[CompuTronix]

room temperature ranges between 19 and 22 degrees.

Prime95
80 degrees
167W

Handbrake
77 degrees
160W

Do you think it would be wise to upgrade my cooling solution to something higher rated? Something like:

Dark Rock 4
Noctua NH-U14S
Noctua NH-D15

Here's the nominal operating range for Core temperature:

Core temperatures above 85°C are not recommended.

Core temperatures below 80°C are ideal.

Core temperatures increase and decrease with ambient temperature, for which the International Standard (normal) is 22°C or 72°F.

Without knowing your location, if your ambient temperatures are typically around the values you previously provided (19 to 22°C), and your worst case workload scenarios are transcoding (77°C) or P95 (80°C), then I see no need for you to upgrade your cooling solution.

However, if you're currently in your cool season and your ambient room temperature increases by 5°C or more, then yes, I would recommend upgrading. The coolers you listed are top-of-the-line, but I would change Dark Rock 4 to the "Pro" variant. Dimensions, price, availability and aesthetics will then determine your choice. As a less expensive alternative, you could delid your 8700K, in which case the resulting decrease in Core temperatures would allow you to continue using your present cooler.

Also, I wanted to mention, as per Intel’s Datasheets, TDP and Thermal Specifications are validated “without AVX”, which is primarily why we run Prime95 Small FFTs with all AVX test selections disabled. See Page 87, Section 5.1.1, 1st paragraph, 2nd sentence:

8th and 9th Generation Intel® Core™ Processor Families Datasheet, Volume 1

CT

 

[ian.egerton]

Here's the nominal operating range for Core temperature:

Core temperatures above 85°C are not recommended.

Core temperatures below 80°C are ideal.

Core temperatures increase and decrease with ambient temperature, for which the International Standard (normal) is 22°C or 72°F.

Without knowing your location, if your ambient temperatures are typically around the values you previously provided (19 to 22°C), and your worst case workload scenarios are transcoding (77°C) or P95 (80°C), then I see no need for you to upgrade your cooling solution.

However, if you're currently in your cool season and your ambient room temperature increases by 5°C or more, then yes, I would recommend upgrading. The coolers you listed are top-of-the-line, but I would change Dark Rock 4 to the "Pro" variant. Dimensions, price, availability and aesthetics will then determine your choice. As a less expensive alternative, you could delid your 8700K, in which case the resulting decrease in Core temperatures would allow you to continue using your present cooler.

Also, I wanted to mention, as per Intel’s Datasheets, TDP and Thermal Specifications are validated “without AVX”, which is once again, why we run Prime95 Small FFTs with all AVX test selections disabled. See Page 87, Section 5.1.1, 1st paragraph, 2nd sentence:

8th and 9th Generation Intel® Core™ Processor Families Datasheet, Volume 1

CT

Cheers again.

I'm in Ireland, so we are in summer (of what we call summer, as it's so crap still ). Room temps will rarely get above the 19 - 22 degrees mark.

 

[CompuTronix]

Perfect! Your thermal performance is adequate for your environment, so stay with your cooler and enjoy your rig!