Question i9 - 9900k reaching 100 degrees in blender viewport render ~

[Pr1mal]

Hey guys,
So I built my pc about a month ago and it's been running just fine but when I switch to render view in blender my cpu instantly goes to 99-100 degrees Celsius. Usually when I am gaming I use ultra settings as I have a high end gpu so my cpu temps usually stay within the 50-60 degree range. I have an NZXT AIO liquid cooler (Kraken x62- 240mm) which is front mounted and my cabinet is the H500 by nzxt which has average airflow (negative pressure). but the radiator fans have cool air coming in so I don't get how my temps are reaching this high within seconds. Could it be poorly applied thermal paste? If so, I don't understand why it doesn't happen while heavy gaming. I even play csgo and that is supposed to use more cpu than gpu and the temps stay normal so I don't get it. Any suggestions would be highly appreciated.
Thanks!
Edit: My CPU Cooler is actually 280mm not 240mm as mentioned earlier.

 

[Lucky_SLS]

Blender is more cpu intensive than games.

The temp you have at gaming loads seems normal to me. Meaning that you have installed ur cooler correct without any mistakes.

Do you have HW monitor or Intel xtu? You can monitor the cpu temp/ core voltage /power draw ect.

Blender used avx instruction, which is cpu intensive. So you can have a negative avx offset to lower core clock and maybe bring down your cpu Temps.

It's better to run at 4.8ghz @ 85c with no thermal throttle than to run it at 5ghz @ 95c with thermal throttling to 700mhz.

 

[Darkbreeze]

Gaming does not use AVX instructions. Blender does, so that could be a factor. Gaming rarely loads a CPU to get anywhere near TDP or full usage, while many testing utilties like Prime95 can apply 100% or higher loads. Anything over 80°C is undesirable. Anything over 85°C is too hot and is getting into the range where damage could begin occuring during long term usage. Anything over 90°C could begin causing immediate thermal fatigue.

You should double check your mount to make sure it is properly flat and perhaps even redo the paste job under the water block. More than likely though, it is simply the fact that your 240mm cooler is not adequate for the thermal design power of the 9900k which honestly requires a larger 280-320mm AIO for extended all core turbo operation, especially if you are running AVX applications.

https://blender.stackexchange.com/questions/1666/how-to-stop-blender-from-making-the-cpu-overheat

i7-7700K runs hot (100°C) under Blender render load despite H100i v2 cooler

I recently completed my first PC build and have been happily working/gaming/3D modeling/yadda yadda, but I've noticed that when I cycles render an image in Blender my CPU's normal operating temperature leaps near-instantly from 30°C (when browsing/playing League of Legends/playing Netflix or...

forums.tomshardware.com

AVX:

https://news.ycombinator.com/item?id=13925039

Blender uses AVX during cycles, so it might be relevant or it could just be a bad mount job or too small of a cooler.

 

[Pr1mal]

More than likely though, it is simply the fact that your 240mm cooler is not adequate for the thermal design power of the 9900k which honestly requires a larger 280-320mm AIO for extended all core turbo operation, especially if you are running AVX applications.

Hey thanks for the reply. My CPU cooler is actually 280 mm i accidentally wrote 240mm. My bad.
I think it must have something to do with the AVX instructions you mentioned. I'll check out the link you gave.
Also, on prime95 blend test I am getting normal temps but on Aida64 CPU and FPU tests it shows that I have around 15-16% CPU throttling. Should I install the cooler again? I have some cooler master thermal paste that I applied pretty generously (not too much tho) so I can use that.

 

[Pr1mal]

Blender is more cpu intensive than games.

The temp you have at gaming loads seems normal to me. Meaning that you have installed ur cooler correct without any mistakes.

Do you have HW monitor or Intel xtu? You can monitor the cpu temp/ core voltage /power draw ect.

Blender used avx instruction, which is cpu intensive. So you can have a negative avx offset to lower core clock and maybe bring down your cpu Temps.

It's better to run at 4.8ghz @ 85c with no thermal throttle than to run it at 5ghz @ 95c with thermal throttling to 700mhz.

Yes I have HWinfo and the temps are usually normal. Even the voltage is around 1.3-1.4 which I think is normal.
I changed the user prefs in blender to use only the gpu and that seems to work and my cpu temps are normal but I want to be able to use both of them together as I think my work would render faster. Correct me if I'm mistaken to presume that. So would a negative avx offset be the only option?
And yeah I think this 5ghz is pointless I'll just drop it down to a normal 4.7Ghz.

 

[Lucky_SLS]

Using cpu or gpu depends on the blender engine itself. Some are optimized to use cpu and some are optimized to use gpu.
You have to check that out yourself.

More than clock speed, temperature, the power output determines the cooling required and the performance of the chip.

Do you have multi core enhancement(mce) enabled? All core 5ghz overclock?

Other than that 100c while using blender, what's the package power draw for the cpu?

It might be that with mce enabled, ur cpu is just running at a high vcore and the temperature spikes. How to identify that?
If the package power draw is less than 100w and the core voltage is 1.4v, the cpu is just asking more voltage to sustain the 5ghz oc on all cores and the temperature rises.

That's why it's best to have a stable tested fixed oc settings by finding the hard limit yourself will be better in this case.

Before Intel 8th gen, per core oc wasn't known much. Everyone oced all the cores to the same ghz.

Intel auto oc applies per core oc settings to achieve those high ghz.

Look at ur core clocks at stock settings to see which cores has the highest turbo clocks. Those give you which cores can oc more.

Then you can stability test those cores by running a cinibench with 1 core(disable other cores in bios and test the limits for each core 1 by 1) at max oc.

Finding the max oc limits and then applying those settings for all cores is the way to go about it. Time consuming and tedious for sure but worth it and gives you a sense of accomplishment if you ask me.

 

[Darkbreeze]

I have some cooler master thermal paste that I applied pretty generously (not too much tho) so I can use that.

How much is "pretty generously"? If you're applying more than necessary it can definitely affect temps, because too much paste starts acting like a thermal barrier instead of just filling the micro pores and any convexity or concavity that might exist. It doesn't take that much. If you sliced the exposed part of a brand new #2 pencil eraser off and then cut it into three equal sections, one of those sections is probably about what you need to add, dead center on the top of the CPU heat spreader.