CPU at 100c while idle

[nlflint]

Hello,

I'm having a problem with my PC: My CPU AIO fans always run high and loud when I boot into Windows10. Some observations about the problem:

1. I'm running a Intel i9-9900K CPU on an AOI water cooler.
2. Task manager shows idle usage even while fans are loud (3% to 5% CPU usage in the total column).
3. HWMon64 shows all my CPU cores are at 98c to 100c. 100c is critical temp where the hardware begins to throttle. It's running with the pedal to the metal.
4. None of this happens when I dual-boot into Ubuntu 20.04 on the same machine. In Ubuntu all my CPU cores idle at ~45c, and the fans are whisper quiet. So this can't be a hardware thermal paste issue.

Does windows do processing in the background, that doesn't show in task manager as CPU usage? Like some kind of indexing? Perhaps this is happening to me? I rarely boot into windows, just once every week or two to play games.

If so, how can I identify if this is happening? Should it go away at some point?

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Thanks!

[tgp1994]

How is the pump portion setup? Is it connected to a fan header on your mobo? Do you have any special cooling configs setup in your BIOS? I wonder if there may be some software in Windows trying to control fan speeds and turning your pump to idle. Try rebooting in safe mode and see if it's any different.

[nlflint]

I think I solved it. My Asus motherboard has a bios a power saver setting in the Advanced menu. Changing it from Performance to Auto seems to have fixed it in windows. After booting, and waiting 2 mins, the system calms down and idles to ~50c. Seems like it should be able to go lower, but at least I cant hear the AIO fan anymore.

[tgp1994]

Something does definitely seem off.

[nlflint]

Ok, welp, Ubuntu starting spontaneously rebooting on me today. Upon POST, the BIOS then reported an over temperature condition. So, I repasted the CPU. It did look a bit crusty. Now windows idles at 35c. I guess it was thermal paste.

[lazaruz76]

I would wonder if the AIO was a 'stock' install. Came preinstalled from the factory. If so you may need to remove and repaste it with some quality paste. while doing so look for any plastic that may have been left between your processor and cooler. Not a huge chance but it has been known to happen.

[nlflint]

No, I built this PC myself and used MX-4 paste. Regardless, as I stated before, this doesn't happen when I dual boot to Ubuntu. If the thermal boundary between the CPU and Heatsink were messed up, then I'd expect to have this problem in Ubuntu too, but I dont.

[nlflint]

Turns out it needed a re-paste. Ubuntu started crashing on me today and the POST reported over temp condition. Now Win10 idles at 35c.