[SOLVED] 9900KS throttles down to 4.5ghz from 5ghz at 70°C

[christopheduron]

When my cpu isn't under any load all cores sit nicely at 5ghz, but as soon as i turn on prime95 they jump down to 4.5ghz while the temperature sits between 65°C-70°C. These temperatures seem a bit too low for it to throttle down. I assume it has something to do with my BIOS settings, but since i'm an absolute amateur when it comes to that i need some help.

If you have any idea why this happens, please let me know! All the information necessary should be within the links below. My apologies for supplying links and not the pictures directly into the thread, but i can't figure out how to get them to show here. Even after following the sticky guide it keeps telling me something went wrong.

EDIT: i tested it during some games and all cores stay at 5ghz also at around 70°C with a load of about 35%. So why does it go down at 100% load with prime95?

Specs:
https://prnt.sc/rurp3s

prime95 = off
https://prnt.sc/rurppg

prime95 = on
https://prnt.sc/rurq6t

BIOS settings:
https://prnt.sc/rurqyr

https://prnt.sc/rurrat

https://prnt.sc/rurrk9

https://prnt.sc/rurrtr

https://prnt.sc/rurs4e

 

[MadsModsat]

I notice you are running the 9900KS on a Z370 series motherboard.

While it is compatible, the power draw of the 9900K and especially the 9900KS can put a lot of load on the VRM design on the z370 series motherboards, which are originally not designed with the two most power demanding CPUs of the 9th Gen series in mind -yours being the most power demanding CPUs of all in the 9th Gen series.

This can result in overheating VRM causing them to throttle the CPU.

The 70'c temperature of the CPU isn't a problem, but if the CPU is at 70'c it could indicate, that the VRM are running very hot as well.
Remember - Prime95, Small FTTs, especially if AVX is on, stresses the CPU and the board power phase design beyond almost anything else, and far beyond any kind of stress you would realistically encounter on an everyday basis.

If you are using a custom watercooling loop or an AiO for CPU cooling, this would further complicate the issue, because of the reduced airflow over the VRM, which would have been present in most situations when using an air cooler.

It is usually recommended to use a z390 series motherboard with solid power design specifically when it comes to the two i9 CPUs, due to the high demand for power.

So while there are no compatibility issues, it is often seen that power draw can be a problem instead, when it comes to the combination of the two i9 CPUs and the z370 series motherboards.
Sometimes people are even suggesting, that the the life span of z370 motherboards can suffer quite severely in a situation like yours. But since I have no personal experience with that specific scenario, I can't say how much of a concern that should be in general.

I looked at your BIOS settings, and nothing really stood out as a problem. But I need look more carefully at them, to be completely sure

But to me, using the z370 board could be a problem that needs to be investigated further, as the cause of the throttling - most likely VRM temperature and load. There are lots of posts on different forums describing similar complications.

I know that the power design is better on some motherboards compared to others, and I have already paid attention to that in my response. Even quality z370 boards are reported to suffer from this - although it is more of a problem if the motherboard has an average power design, of course

Another possible problem could be power throttling rather than thermal throttling. With that in mind, what PSU do you have? Make and model + age?

Usually there's a setting in BIOS to allow increased power draw. It has been a while since I had a MSI board, so I don't remember what that setting is called, or if it is available

But to be honest, I would personally begin by looking at possible VRM temperature problems

I suspect the combination of a z370 board, the most power demanding CPU of all compatible with that board (but not designed for), and Prime95 is simply too much strees to put on the system

 

[christopheduron]

Thank you for such a well written reply.
After some looking around a few other people mentioned something about VRM possibly overheating or power throttling. I'm just not sure how i can test those things. As far as i know there are no VRM temperature monitoring programs?
My PSU is only a few months old: 'corsair-600w sf600 sfx 80+ gold modular'. It's just a temporary psu keep in mind and i will get one around 750w eventually. Again, is there some way to test the power draw of your complete system to check if i reach the 600w cap when turning on prime95?

 

[bignastyid]

It's the AVX offset. When running AVX instructions(prime95 uses AVX) the system will down clock to that offset.

Your screenshot currently has that set to auto(on many boards auto its seems to go to ~5). So when you run an AVX instruction set with an offset of 5 it will take the multiplier(50 in your case) and subtract 5(so you'll have a multiplier of 45).

You can adjust that, but it will produce alot more heat and use more power the lower the offset number is.

 

[MadsModsat]

Unfortunately it is not really a very common feature to have VRM temperature sensors. I believe some AMD x570 bords have taht feature.

So you would need a device which can read temperatures by placing sensors in various spots on the VRM, or something like an infrared thermometer like the ones that can measure body temperature in the ear.

I should have been more precise when I mentioned power throttling. Although the PSU is important to include when troubleshooting possible power related issues, what I actually had in mind, is that some motherboard has a defaullt BIOS setting, which limits CPU power draw to a certain number.

My own ASUS motherboard, actually throttles the stock i9 9900K quite a lot, because ASUS sticks very closely to Intels specified 95 TDP.

SO even with all requirements met, the 9900K throttles hard on my board. To remove t hat limit, there is a simple BIOS setting, and then everything runs perfectly fine.

Inmy own experience, this is not something I have run into on an MSI motherboard, I mostly mentioned it, because that could be something to look into, if the VRM temperature is not the issue.

If you complete system lacked power, I suspect a hard crash with BSOD would be an issue, or GPU related crashes, since it is very commonly seen in situations with poor power suplly.

 

[MadsModsat]

It's the AVX offset. When running AVX instructions(prime95 uses AVX) the system will down clock to that offset.

Your screenshot currently has that set to auto(on many boards auto its seems to go to ~5). So when you run an AVX instruction set with an offset of 5 it will take the multiplier(50 in your case) and subtract 5(so you'll have a multiplier of 45).

You can adjust that, but it will produce alot more heat and use more power the lower the offset number is.

Are you sure the AVX Offset for the KS CPU isn't 0?

That seems to be in the default specs

But it is set to Auto in OPs post, so it could very likely be an issue

 

[bignastyid]

Are you sure the AVX Offset for the KS CPU isn't 0?

That seems to be in the default specs

AVX offset it set by the bios not the CPU.

 

[MadsModsat]

AVX offset it set by the bios not the CPU.

Yes, I'm aware of that. Although exceptions are seen, in my own experience, Auto settings more often than not, defaults to CPU factory settings, apart from voltages, which seems to be set a bit high on many ocations

But I'm not trying to dosmiss your explnation at all, it looks like a very possible solution to the problem

And the reason for asking, is that I can always learn new things as well

 

[bignastyid]

Yes, I'm aware of that. Although exceptions are seen, in my own experience, Auto settings more often than not, defaults to CPU factory settings.

But I'm not trying to dosmiss your explnation at all, it looks like a very possible solution to the problem

I have yet to see or hear of a 300 series motherboard that used a default/auto setting of 0 for the AVX offset. Where are you seeing the 0 default for the 9900ks?
Intels site only shows AVX2 support in the specs nothing about a default offset.
https://www.intel.com/content/www/us/en/products/processors/core/i9-processors/i9-9900ks.html

 

[MadsModsat]

I have yet to see or hear of a 300 series motherboard that used a default/auto setting of 0 for the AVX offset. Where are you seeing the 0 default for the 9900ks?
Intels site only shows AVX2 support in the specs nothing about a default offset.
https://www.intel.com/content/www/us/en/products/processors/core/i9-processors/i9-9900ks.html

It is something that is mentioned in reviews, I'd be lying if I said anyone from Intel confirmed it to me personally.

Here's a quote from KitGuru
"The Core i9-9900KS does 5GHz under AVX loading out of the box."


I must have been exceptionally lucky with my motherboards, if no BIOS generally set the factory AVX offset corret.

On my own board, loading optimzed BIOS settings, in the upper left corner, the BIOS shows an AVX target frequency with no offset, and AVX is set to Auto.

I've only owned two different z390 boards, so with that limited number in mind, I can't say what's is most commonly seen.
But I've been lucky twice with my z390 boards, so naturally I'm surprised it is as uncommon as you say, to see a factory AVX offset being correct.

But I'm not trying to argue, I think you have a very good suggestion when it comes to a solution to OPs problem. So I'm a bit unsure what we are debating?

I haven't claimed anything anyone said to be wrong, and I always make sure to inform people when my own personal experince is what I base my suggestions on, and I never state anything as a fact, if I don't know

 

[christopheduron]

It's the AVX offset. When running AVX instructions(prime95 uses AVX) the system will down clock to that offset.

Your screenshot currently has that set to auto(on many boards auto its seems to go to ~5). So when you run an AVX instruction set with an offset of 5 it will take the multiplier(50 in your case) and subtract 5(so you'll have a multiplier of 45).

You can adjust that, but it will produce alot more heat and use more power the lower the offset number is.

AVX instructions are completely unknown to me. I'll try turning that value to 0 to test if prime95 still makes me throttle down. Are those instructions something that's commonly used? I honestly only use my pc for gaming, so if it's not important for games i may just leave it on auto.

 

[alceryes]

I've got a i9-9900k on a Z370 Gaming Plus and can also attest that, according to HWiNFO64, my VRMs hit their thermal threshold before the CPU does. This is during stress testing. I've had my chip up to 5Ghz but I have to put more voltage than I'm comfortable with through it.

Also note that just because the thermals don't appear to be too high this doesn't guarantee that your chip can do more. Every piece of silicon is different. Thermals are just ONE of several factors deciding how high you can go.

 

[bignastyid]

AVX instructions are completely unknown to me. I'll try turning that value to 0 to test if prime95 still makes me throttle down. Are those instructions something that's commonly used? I honestly only use my pc for gaming, so if it's not important for games i may just leave it on auto.

Just make sure to watch temps with it at 0. According to reviews the 9900KS is capable of it, but your motherboard may not be.

 

[christopheduron]

It's the AVX offset. When running AVX instructions(prime95 uses AVX) the system will down clock to that offset.

Your screenshot currently has that set to auto(on many boards auto its seems to go to ~5). So when you run an AVX instruction set with an offset of 5 it will take the multiplier(50 in your case) and subtract 5(so you'll have a multiplier of 45).

You can adjust that, but it will produce alot more heat and use more power the lower the offset number is.

Hey, thanks. The avx setting seems to be what i was looking for. I changed it to -4 and when running prime95 all clocks are sitting on 4.6ghz. So it seems that the auto function has a value of -5.
I use my pc almost exclusively for gaming; do you have any idea if those avx funtions are being used in games nowadays? If not, i don't see any reason why i shouldn't keep it on auto.

 

[MadsModsat]

Glad to hear that was the solution, I'd say that's pretty much the best case scenario

Very few games use AVX instructions - the only one I can remember without searching is Battlefield V, which is supposedly using AVX instructions.

I write supposedly, because there's no official statement that I'm aware of which is confirming it, but on the BF V forums it is referred to almost as a fact. There's plenty of indications it is true, and I'd say it is probably correct.
It is mostly overclockers who brought it up, because their overclocked CPU runs at the AVX offset frequency when playing BF V

There are a couple of other titles as well, but it is not something which is seen very often so far - I have no clue to what direction it might change in the future for upcomming game titles

An AVX offset of 5, puts it lower than the 9900K, it is a big offset since the CPU is supposed to be fully capable of 0 offset on stock settings, but there's nothing wrong with it at all.

Leaving it on Auto, shouldn't cause you any further problems, in my opinion. Unless Auto suddenly decides on a different offset, which would be quite surprising if it did, you should be just fine