Question New Build - I9-9900K High CPU Temp

Oct 14, 2020
Hi Guys,

I'm after some of your expert advice if you'd be so kind please. I've recently put together my first build and it's certainly been an eye opening experience! I last built a PC in 1994 (yes, I'm old!) and to say things have moved on a little is an understatement. So, apologies in advance for being a complete noob or erm, washed up? :)

I think I, by luck more than judgement, appear to have built the following system:

Core components:
Case - CoolerMaster Cosmos C700m
Motherboard - Gigabyte Z390 Aorus Ultra
CPU - Intel i9-9900K
Corsair H150i RGB Pro XT
GPU - (MSI 3080 pre-ordered) - currently using my old MSI Gaming X 1080TI for the moment

All seems generally to be OK with the system with the exception of the CPU temps. I'm running the system completely stock with no OC. When playing something like Battlefield 5, for instance, I'm touching 80 degrees Celsius and if I run something like Prime95 on the smallest test I'm hitting 90+ literally within a couple of seconds of kicking the test off.

Idle temps are around 29-30. This is measuring with Core Temp. GPU temps are also pretty low even when gaming.

In terms of the configuration of fans and stuff, the case comes mounted with 3 x 120mm in the front of the case pulling cold air in. I then have a 140mm fan at the rear as an exhaust and I've mounted the H150i in the top of the case with the 3 x 120mm fans pushing air up through the radiator and out the top of the case.

I initially mounted the cooler with the default paste that came with the H150i, but I have since replaced this with an aftermarket thermal paste. I've tried reseating the cooler and it looks nice and snug.

In the Corsair iCUE software I can see the pump is working RPM wise. If I set the profile to 'extreme' the fans get a little bit more angry and the temps come down by a couple of degrees, but it still seems wildly out of control.

One observation I did make, if I touch one of the tubes I can feel it vibrating, hence the pump is working, but if I feel the other tube I can't feel any motion through it. If it's a closed circuit presumably I should be able to feel some sort of vibration through both tubes?

Any idea what might be going on please outside of a possible blockage in the AIO (if my understanding is correct on the above point)?


Battlefield 5 is one of those titles that actually uses AVX instructions - if I remember correctly - so it's kind of an extreme case. 80C would be fine.

Prime 95, Small FFT - not the smallest - and all 3 AVX settings off, are the settings to use for testing cooler performance. Me thinks you used the wrong settings here.
Reactions: CompuTronix
Oct 14, 2020
Thanks for the reply Sir. So, I could of been panicking over nothing. I've just re-run Prime95 on small FFT with the 3 checkboxes to disable AVX checked and I'm sitting around 71-73 degrees.

Would you say that is about normal?