Setting CPU Power Limit values in BIOS

[SardusX]

Hi All,
Reading the Noctua CPU compatibility list, I noticed about the Intel CPU 9th generation (i.e. i9-9900k) for some models (i.e. NH-U9S, NH-U12S) the following warning:
“if power limits are disabled in BIOS, CPU might not be able to keep maximum turbo clock under prolonged AVX loads, suggested maximum power limit: 195W”.
How to set these limits correctly in the BIOS, following this warning (i.e. in a small form factor system)?
Is it possible to estimate which performance limitations, for example in percentage compared to a use without limitations (obviously with a more performant CPU air cooler model), would this cause?
Thanks in advance for your advice.

 

[pastrychef]

Hi All,
Reading the Noctua CPU compatibility list, I noticed about the Intel CPU 9th generation (i.e. i9-9900k) for some models (i.e. NH-U9S, NH-U12S) the following warning:
“if power limits are disabled in BIOS, CPU might not be able to keep maximum turbo clock under prolonged AVX loads, suggested maximum power limit: 195W”.
How to set these limits correctly in the BIOS, following this warning (i.e. in a small form factor system)?
Is it possible to estimate which performance limitations, for example in percentage compared to a use without limitations (obviously with a more performant CPU air cooler model), would this cause?
Thanks in advance for your advice.

I'm unaware of any way to estimate power limit. I think you will have to do your own trial and error testing.

That being said, I've done a build using the NH-U9S and I would not recommend it for use with an i9-9900K. I used it with an i7-7700K and found it to be just adequate.

I haven't used the NH-U12S, but, if I had to guess, I would think that it should be sufficient for an i9-9900K if you don't overclock.

 

[SardusX]

Thanks for sharing your experience,
about the NH-U12S, Noctua CPU compatibility list recommends to limit to 205 w Power limit value to prevent excessive temperature increases due to the turbo frequencies and not only in case of intentional overclocking, if I understand correctly.
Can the power limit value be correctly set by intervening on the PL1 and PL2 values in the bios configuration?

 

[pastrychef]

Thanks for sharing your experience,
about the NH-U12S, Noctua CPU compatibility list recommends to limit to 205 w Power limit value to prevent excessive temperature increases due to the turbo frequencies and not only in case of intentional overclocking, if I understand correctly.
Can the power limit value be correctly set by intervening on the PL1 and PL2 values in the bios configuration?

At stock speeds, I highly doubt you will ever reach 205W no matter how much you stress the CPU. It's only when you start overclocking that you can reach such high values.

With my personal i9-9900K, full system draw goes from approx 104W at idle to about 308W under full load when running Prime95. This is with the CPU overclocked to four core 5.1GHz and four core 5.0GHz with 1.31v. This means that with just 1.31v it's exceeding 205W.

I use a Noctua NH-D15S with two fans mounted to it. With this overclock, my CPU maxes out at 85C when running Prime95 and runs a few Celsius lower when doing Handbrake video conversions. Idle temps fluctuate a bit with ambient temps but are typically around 37C or lower.

Disclaimer: My particular i9-9900K is delidded and Conductonaut is used in place of the STIM.

As you can see, with the i9-9900K, even a modest overclock can increase power draw dramatically. The NH-D15S I use is significantly larger than the NH-U12S too. However, I was relatively conservative in trying to keep temps at 85C or lower because the i9-9900K Intel spec has TJMax temp of 100C.

Theoretically, you should be able to use PL1 and PL2 to limit power but I've never used these features and can't comment on how effective they are.

 

[SardusX]

Sorry if I add an apparently off topic question that comes from your in-depth explanation. This thread also arises from my perplexity regarding the use of air-coolers with considerable weight and size: since you have a direct experience it can be the weight of the Noctua nh-d15s being a problem for the motherboard and the CPU in a system mounted in a mid-tower case?

 

[pastrychef]

Sorry if I add an apparently off topic question that comes from your in-depth explanation. This thread also arises from my perplexity regarding the use of air-coolers with considerable weight and size: since you have a direct experience it can be the weight of the noctua nh-d15s being a problem for the motherboard and the CPU in a system mounted in a mid-tower houses?

I've been using the same NH-D15S for several years now, first with an i7-6700K, then i7-7700K, then i7-8700K, and now with my i9-9900K. Its size and weight has never been an issue for me. It's extremely maintenance free and I've only had to dust it out every few months (my apt is abnormally dusty...) with some compressed air.

The NH-D15S has done a great job of cooling my CPUs (all of which were overclocked). It also remains very quiet with the Noctua fans. One added benefit to using an air cooler such as this is that the fan(s) mounted on the heatsink moves air around the VRM heatsinks which helps keep them cool. This is something that's almost never mentioned...

I have never found myself wanting or even considering switching to water cooling due to how well the NH-D15S performs. I can't send it enough praise.