8086k overclocking adventure on air

[Voodoo Rufus]

So I got new toys to play with. Gigabyte Aorus Master mainboard, 8086k delidded Silicon Lottery CPU, using a Dark Rock Pro 4 heatsink.

I left everything on auto, set the CPU wattage limit to 250W, and then started jacking up the multiplier. The mainboard automatically ramped CPU voltage depending on the clock rate, pretty aggressively once I got past 4.6GHz. Did some 30-45 minute prime95 runs to test initial stability. I manually played with the fan settings to get a good balance of noise/airflow/temps. After 70C I have the CPU and chassis fans running 100%, which is still a low hum. Anything under 60C is nearly silent.

Anyway, on 5.0GHz I needed 1.32V in bios (LLC set to 6) to get it stable in a short term sense. I had it crash out a few threads after 6 hours. What puzzles me is that depending on the P95 task type, the CPU will either stay nice and happy around 65-70C and a calculated HWMonitor CPU wattage of 150W, or ramp up to 200W and 85-90C (ouch), like a switch. It will bounce between the two every 15 minutes or so. The clocks are not throttling, but the VID drops from 1.35V to 1.28V, while the Vcore maintains at 1.36V.

What's going on here with the temp and wattage switching?

 

[Voodoo Rufus]

Just learned that I should use the AVX offset on this to lower the temps on those tasks.

Back to overclocking school for me on this chip.

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Just learned that I should use the AVX offset on this to lower the temps on those tasks.

Back to overclocking school for me on this chip.

 

[larryccf]

that was what i was going to ask you, ie what AVX offset you were running

i'm not a world class OCer, but MSI has a heck of good OC by the numbers guide with a couple of setting tweaks i hadn't seen before
https://www.msi.com/blog/intel-9th-cpu-overclocking-5ghz-with-z390-motherboards

 

[wingman99]

Prime95 going from large calculations to small using more system memory than cache.

 

[mackerel]

Prime95 as a stress test will switch between different FFT sizes. Smaller FFTs will fit inside the CPU's cache and will fully load the cores, generally resulting in higher temperatures. Large FFTs will become limited by ram bandwidth. In that case, you would see lower CPU core temps, but there is more stress on IMC for example.

 

[EarthDog]

Sounds like P95 being P95...

 

[Voodoo Rufus]

Yeah, and you can manually enable or disable AVX tasks by altering one of the P95 text files. That way one can stress test AVX tasks or not to test both sides of the stability.