Clocks are slowing down on i9-9900K during stress tests
Clocks are slowing down on i9-9900K during stress tests
So according to the title, my clocks continue to drop on my 9900K during stress testing in Prime95 Smallest FFT. I'm not even overclocking yet, just aiming for a stable 5GHz across all cores without any AVX offset. I'm using an ASRock Extreme4 Z390 Mobo and a 16GB G.SKILL Trident Z RGB 3000MHz. I'm not applying XMP profiles but am using the right timings and voltages.
I'm not encountering any errors in Prime95, though I've set the TJ max to 105°C just for stress testing since the actual TJ max is 115°C. However, to run without errors in Prime95, I sometimes have to push the core clocks up to 1.4 vcore, reaching 1.440 occasionally when AVX is enabled. This happens even with AVX disabled in Prime95, where core clocks start dropping and voltage decreases. It's really confusing, so any advice would be appreciated.
Additionally, during an Intel Burn test at Very High Stress (because I don't have enough RAM for the maximum), it stays stable at 5GHz and 1.424 vCore without issues. Please help!
Not yet pushing it too hard, just checking if it can hit 5 GHz across all cores...
Running every core at full turbo (MCE mode) definitely goes overclocking.
Not every 9900K will keep 5 GHz stable on all cores, especially with temperatures above 1.4V... who knows what cooling setup is needed? (How can we talk about 9900K core temps without mentioning the cooling solution?)
Many motherboards have BIOS power limits that mostly follow Intel guidelines, allowing a certain turbo for about 30 seconds before automatically downclocking to reduce power use to roughly 95–125W.
At all-core operation at 5 GHz, the actual power consumption is probably between 130 and 145 watts.
You might have to disable those power limits, easy...
What was the CPU temperature during the test? What is the make and model of the PSU?
Not yet pushing it too hard, just checking if it can hit 5 GHz across all cores...
Operating every core at full turbo (MCE mode) definitely goes beyond normal overclocking,
Because not every 9900K setting will keep 5 GHz stable on all cores, particularly when temperatures climb above 1.4... who knows what cooling is needed? (How can we talk about 9900K core temps without mentioning the cooling solution?)
Many motherboards have BIOS power limits that mostly follow Intel guidelines, allowing a certain boost for about 30 seconds before automatically lowering the speed to reduce power use to roughly 95-125W...
In reality, achieving all-core 5 GHz would draw around 130-145 W...
You might need to disable all power restrictions easily—just through Intel's XTU tool...
Running a full load with the latest Prime95 is still manageable (though not trivial), especially when AVX is disabled and only a few FFTs run. Turning AVX on increases the workload significantly, similar to an 110-120% stress test, which often leads to temperatures becoming unacceptably high... (unless you have liquid nitrogen available)
Therefore, try your tests again as suggested, and observe the temperatures under more typical conditions rather than pushing the CPU to its absolute limit. This is why AVX adjustments exist—helping to lower clock speeds and control heat and power consumption!
What clock rates does the CPU reach during stress testing? As mentioned earlier, an all-core 5GHz frequency on an i9 9900K can only be reached through overclocking. Even though your aim is a zero AVX offset, many users have to implement an AVX offset to maintain performance at that speed. Of course, this is possible—many have already demonstrated it—but it doesn’t work in every configuration. If you require a very high voltage to run a 0 offset AVX, you should weigh whether the performance benefits justify the extreme voltage needed, or consider lowering the core voltage by adding an AVX offset. A Vcore of 1.44 falls into the upper range for a 5GHz 9900K build (though not exceeding Intel’s specifications), and for anything beyond a standard benchmark machine, it’s a high Vcore for someone who uses the PC daily. I’m impressed if you can manage to keep temperatures stable at that voltage—it suggests you have excellent cooling. Definitely worth exploring further. My ASUS motherboard restricts CPU performance significantly even with default settings; if I bypass BIOS and adjust power limits, and remove restrictions on exceeding the 95W TDP spec, my 9000K can sustain boost clocks for as long as necessary. Some adjustments are handled automatically when XMP is enabled, so if you’re not using the XMP profile, it might be useful to note what changes it makes in BIOS—voltage and current settings affect RAM stability, among other factors.