8700k 5Gz OC Considered Stable?

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echoes1991

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Oct 29, 2018
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Hi, everyone. I'm pretty new to this, but I think I've done everything correctly thus far. These are my current specs.
Asus ROG Strix Z390-E
i7 8700k OC to 5.0ghz no delid
64gb Corsair Vengeance RGB Pro 3000mhz 15-17-17-35
EVGA FTW 3 Hybrid 1080ti.
NZXT Kraken x62 with 2 EK-Furious Vardar Evo 140mm fans in Pull configuration
Seasonic 750w Fully Modular 80+ Gold PSU

When I first got this processor, I immediately established a baseline at the out of the box settings at 1.3v.
I found baseline stability as low as 4.7ghz at 1.230v.
Seems like I got lucky with the purchase. I've managed to OC to 5.0ghz at 1.290v with AVX offset of 0 and LLC of 6. I successfully passed 8 hours (7hrs and 52 min) of Prime 95 26.6 small FFTs, Intel Burn Test, 10 passes at max. Asus Real Bench, and 5 hours of Aida 64( i know it's a bad stess testor) Memtest also passed overnight no issues.
However, If I run newer versions of Prime 95 with AVX disabled in the config, The workers will start failing after just a few hours in addition to the temps almost reaching 100c

Should I consider this OC stable? or should I be able to pass newer versions of P95) despite the horrendous temperature?
https://imgur.com/a/UUyZs8a

 
Solution
CompuTronix

RealBench runs AVX for which it's necessary to use an AVX offset. Silicon Lottery clearly states on their website and in your shipping spec sheet that they use an AVX offset of 2. Provided you have no other system instabilities such as with memory or GPU overclocking, RealBench should pass with an AVX offset of 2, as Silicon Lottery uses RealBench for testing processor stability.


Respectfully, that blanket statement is incomplete. Please be more specific...
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CompuTronix

CompuTronix

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echoes1991,

If AVX is truly disabled in later versions of Prime95 such as 27.7 through 29.4, then the workload, power consumption and Core temperatures should be identical to non-AVX version 26.6. As you're using Hardware Monitor, click on the + next to "Powers" so you can observe your power consumption (Watts), which is crucial information. Core temperatures respond directly to power consumption, which is driven by workload.

If you entered the character string correctly in the local.txt file, it should consist precisely of:

CpuSupportsAVX=0

If there's a mistake in your local.txt file ... it means AVX is in fact not disabled, and you're unknowingly running an AVX version of Prime95 without using an AVX offset (downclock), which is evidenced by very high power consumption (Watts). If this is the case, then the instabilities and extreme thermal behavior you're seeing is normal and expected, unless you further increase Vcore to compensate for instabilities, which will further increase power consumption resulting in instantaneous throttling at 100°C.

It was discovered after the launch of Core i 4th Generation Haswell processors, that AVX imposes an absolutely brutal overload, which prompted Intel to release the following document cautioning users against using AVX versions of Prime95 ... read down through the 4th bullet, which still applies through today's 9th Generation: Troubleshooting i7 4790K / i5 4690K Overheating - https://forums.intel.com/s/feed/0D50P0000490ohHSAQ?language=en_US

The potential thermal severity of AVX workloads is precisely why AVX offset has been included in BIOS since 6th Generation processors. If you must run a Prime95 AVX version, then an AVX offset of at least 2 or 3 or more will be needed, so that power consumption and Core temperatures don't skyrocket above non-AVX version 26.6, and stability is maintained.

Keep in mind that as per Intel’s Datasheets, TDP and Thermal Specifications are validated “without AVX”.

See page 87, Section 5.1.1 Thermal Considerations, 1st paragraph, 2nd sentence: 8th and 9th Generation Datasheet, Volume 1 - https://www.intel.com/content/www/us/en/products/docs/processors/core/8th-gen-core-family-datasheet-vol-1.html


Real-world AVX apps do not approach the brutal AVX overload imposed by Prime95 versions with AVX such as 27.7 through 29.4.

If you don't use AVX apps, then there's no need to test for AVX stability or thermals.

If this is the case, then your rig is stable.

CT :sol:
 
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1LiquidPC

1LiquidPC

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Oct 11, 2014
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Looks fine to me based on your testing. More than I typically use, at least timewise for each testing program to validate an overclock. Been running my 8700k OC'd since launch. Tried something different this upgrade and had mine delidded and tested at Silicon Lottery. Their numbers are pretty accurate overall for voltage. They add a little voltage as a buffer and listed 1.4v on the supplied result sheet. I need 1.385v for 5Ghz and 0-AVX offset and LLC6. Tried 5.1, but was a no go for Realbench. I personally don't bother with Prime95 these days, as mentioned above it's a power hog and not good for long term health of modern CPUs from AVX loading it utilized.
 
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CompuTronix

CompuTronix

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RealBench runs AVX for which it's necessary to use an AVX offset. Silicon Lottery clearly states on their website and in your shipping spec sheet that they use an AVX offset of 2. Provided you have no other system instabilities such as with memory or GPU overclocking, RealBench should pass with an AVX offset of 2, as Silicon Lottery uses RealBench for testing processor stability.


Respectfully, that blanket statement is incomplete. Please be more specific so our members and readers aren't misled or confused by conflicting information.

For the benefit of those who are unaware, the AVX issue with Prime95 is strictly VERSION dependent. There's a distinct difference:

Later versions of Prime95 such as 27.7 through 29.4 run AVX, which is a brutal overload at nearly 130% that's extreme beyond any other utility. Version 26.6 is non-AVX and runs a true 100% workload:

• Prime95 v26.6 - http://www.mersenneforum.org/showthread.php?t=15504

As per Intel’s Datasheets, TDP and Thermal Specifications are validated “without AVX”.

See page 87, Section 5.1.1, first paragraph, second sentence:

8th and 9th Generation Intel® Core™ Processor Families Datasheet, Volume 1 - https://www.intel.com/content/www/us/en/products/docs/processors/core/8th-gen-core-family-datasheet-vol-1.html

For the record, there is nothing wrong with Prime95 VERSION 26.6.

"Stress” tests vary widely and can be characterized into two categories; stability tests which are fluctuating workloads, and thermal tests which are steady workloads. Intel tests their processors at a steady 100% TDP workload to validate Thermal Specifications.

Prime95 version 26.6 Small FFT's is ideal for CPU thermal testing, because it's a steady 100% workload with steady Core temperatures. No other utility so closely replicates Intel's workload test conditions.

Utilities that don't overload or underload your processor will give you a valid thermal baseline. Here’s a comparison of utilities grouped as thermal and stability tests according to % of TDP, averaged across six processor Generations at stock settings rounded to the nearest 5%:

All tests will show 100% CPU Utilization in Windows Task Manager, which indicates processor resource activity, not % TDP workload. Core temperatures respond directly to Power dissipation (Watts), which is driven by workload. Prime95 v26.6 Small FFT’s provides a true and steady 100% workload, so if Core temperatures are below 85°C, then your processor should run the most demanding real-world workloads without overheating.

The information I've provided concerning Prime95 is from Sections 11 & 12: Intel Temperature Guide - http://www.tomshardware.com/forum/id-1800828/intel-temperature-guide.html

You might want to give it read.

Regarding Silicon Lottery, I completely agree with you; they do a great job. I've purchased several delidded and binned processors from them over the years for various overclocked builds and have always been pleased with their processors.

CT :sol:
 
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Solution
1LiquidPC

1LiquidPC

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Thanks for providing the very detailed information regarding Prime95. Yes, 26.6 is the last recommended version for stresstesting before it's specific AVX testing. I should have been a bit more clear in my previous post. Also, you are again correct on SL info sheet recommending AVX offset of -2. My CPU was "binned" at 5.0Ghz in their testing. In my experience though, I found an issue with the offset that others had as well. By enabling the AVX offset, even light loads such as web browsing or just opening folders in Windows, the CPU would kick down to 4.8Ghz from the offset. I recorded this behavior in gaming as well. It was my understanding that only running AVX based system loads this would occur. I have always chose to run my OC with speedstep, C1E, ect. disabled so I would be at the full 5.0Ghz. I found that by disabling the offset, this 4.8 to 5.0 fluctuation disappeared. Otherwise, I would have left the AVX Offset enabled.

In general, I'm sure everyone who OCs will run different benchmarks/stresstests to verify stability. It's just I personally haven't used any version of Prime95 for last few generations. On a side note regarding Silicon Lottery, I would certainly recommend them as well for those interested. I got my 8700k at launch from a reseller, sent to them for delid/binning. When I received back, there was really no evidence other than the retail box seal being broken that they ever delidded and tested it. I carefully inspect things like this, as I work with circuit boards for a living anyways.
 
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CompuTronix

CompuTronix

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Very astute observation. There are certain motherboard makes / models / BIOS versions where AVX offset doesn't work at all ... OR ... auto works but manual doesn't ... OR ... manual works but auto doesn't. Although AVX offset was introduced with 6th Gen, more often than not it works as advertised. Nevertheless, OEM's have had a few years to fix the bugs, yet there are instances where it still doesn't work properly. However, sometimes a BIOS update corrects AVX offset abnormalities.

To be more specific, the AVX issue actually involves AVX2, and more recently AVX512 on certain High End Desk Top (HEDT) X-Series and Extreme processors. Earlier processors such as 2nd and 3rd Gen are minimally affected by the original AVX Instruction Set, which is not nearly as severe as AVX2.

Unfortunately, there's a lot of 4th Gen Haswell / Devil's Canyon processors in the wild that will never benefit from AVX offset, bugs not withstanding. The only work-around that 4th Gen overclockers can use is to configure a BIOS profile for AVX apps, and another for non-AVX apps and gaming. It's a bit cumbersome to re-boot, but for AVX users who also game, it's better than living with a constant downclock that handicaps CPU performance just to accommodate AVX.

Many gamers / encoders running the 4790K can relate. The 4790K remains an excellent 22 nanometer gaming CPU with a relatively high 4.0GHz base clock, where the 14 nanometer 6700K and 7700K comparatively offer disappointingly little IPC or overclocking advantages.

CT :sol:
 
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1LiquidPC

1LiquidPC

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Oct 11, 2014
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Thanks again for the informative post with the specifics on AVX issues. Learned some things today regarding AVX2 and AVX512 from the HEDT segment. Also, that would be a bit of a pain for AVX app profiles though better than nothing. I figured it was certain boards/UEFI versions and not everyone encountered the bug. At the time, I was using the latest UEFI. It was a few months after 8th Gen launch until I had everything fully up and running. I had sent the CPU early to SL to be sure it was done. After I disabled the offset, I went on to further test my OC. I ended up getting things dialed in otherwise, and never really looked back at the offset issue. The only program I use that I believe uses AVX is the cycles render option when I occasionally make something in Blender. I also use this in my OC testing.
 
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