New 8700k Build CPU Temperature Fluctuations

Minitany

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May 10, 2014
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I just completed a brand new build with a new 8700k processor and have it liquid cooled. I haven't even tried to OC it yet till I knew everything was stable and working. On my particular motherboard I only had 3, 3-4 pin fan connectors due to it being mini ITX. They were labeled as Chassis fan, AIO (liquid cooler), and CPU. According to the manual if you are using a liquid cooler for the CPU you should plug it in to the AIO plug on the board. This left me to plug in my GTX 1080ti liquid cooler fan into the CPU slot and my main airflow 200mm fan in the front to bring in air in the chassis fan plug. When I am just idle in windows or even just web browsing my cpu on different cores will fluctuate rapidly from just 30~ degrees to almost 60 degrees. This will last all of a second, it causes my GPU fan to drastically increase speed (PWM) and then throttle back down. It does this off and on consistently every few mins. I find it highly annoying and am at a loss for what the problem is. I installed a Corsair H100i v2 and right now it is idling at 34-36 degrees. I used MX4 thermal paste (pea size amount) and I double checked to make sure the cooler was attached firmly with no movement.

I tried searching online but it looks like no one else is having this same issue. Does this sound normal? When gaming my loads seemed fine, no heat issues, but I havent captured what my temps are while gaming. I have listed my parts below, any and all help is very appreciated. Thanks for yous time!

Phanteks Enthoo Evolv Mini ITX
8700k i7
16 GB G Skill Trident Z DDR4 3200
Asus Z370 - I Motherboard
Corsair h100i v2 liquid CPU cooler
EVGA G2 750 Full modular PSU
MSI Sea Hawk X GTX 1080ti
Toshiba OCZ 960GB SSD
Crucial 250GB SSD
WD 1TB 7200rpm Sata drive
Also all 120mm fans on the AIO cooler and cooler on the GTX card have been replaced with Corsair ML120 Magnetic levitation cooling fans

Pictures:
https://imgur.com/a/7b5TJ
 

fredfinks

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Oct 21, 2015
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It appears that the mobo is trying to cool the CPU via the CPU header, making your GPU fan spin up.
Maybe they meant if you have an AIO CPU cooler use the AIO header and leave the CPU header empty. (not considering people may have 2x AIOs)

Id swap them around (CPU cooler to cpu header) and contact Asus.
 
Nice build :) You can try and manually adjust the PWM settings to "stretch" the fan speed adjustments. I use AI Suite software for this to adjust my pump speed. This prevents rapid temp fluctuations from ramping things up and down constantly. Regarding temps, these fluctuations are going to be normal due to Intel's TIM and the wide range of turbo clocks and die size. The 7700k had similar fluctuations.
 

Minitany

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May 10, 2014
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Thank you! :)

The AIO with the way it is plugged I cant control the PWM fans(3 pin not 4 pin), so I ordered two splitters so I could accomplish this. I was also thinking of doing on the main air intake fan and splitting it with the GPU. This would then leave the CPU fan plug empty and I was in more control. Thoughts?

Good to know the 7700k did the same thing, I was surprised because I went from a 4790k to a 8700k. I have to say though this has been the best upgrade I have ever done. I am playing FFXIV on max settings (not 4k) at 2560 x 1080 144hz, CPU is hanging around 55 to 60 degrees, GPU has been about 70 degrees. I still think I have some tweaking to do.

 
Spliters is the way to go...And your suggestion of spliitng intake with GPU should work. Though you should be able to set the CPU fan profile in the bios to the case fan...good luck on the monster SFC system.
 

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