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CPU gone crazy (possibly due to mobo)

Level 7
So for the past two days, my CPU has been going crazy on me. Yesterday, I started hitting 100ºC instantly on Prime95 26.6 100% load torture test. I originally thought that the issue was something to do with the cooling setup, so I remounted the heatsink with AS5, which didn't work. Eventually, I found out the issue was that I had in BIOS changed the power options to ASUS ROG optimized mode or something, which automatically upped the Vcore by a little bit. After I changed it back to normal settings, I got 80ºC after only 2 minutes of torture testing, which is slightly better, but I used to get 70ºC after 2 minutes. Ambient temps hover around 28ºC, and I get idle temps at around 32ºC, which is fine. I'm concerned about max load temps. At 40% load, I'm not even hitting 40ºC. In addition, it now boots at 4.0GHz and then slows down and levels off at 800MHz even a dead idle, instead of ~100MHz and I can't seem to change it back, even after loading optimized defaults in BIOS. I have a Corsair H55 push/pull, i7 4790k, and a VII Hero mobo. Can someone please explain what is going on, and how I can get my CPU to work normally again? It was working fine a few days ago, and I believe it might have to do with voltage and CPU speed, instead of cooling. I tried clearing the CMOS and changing the power saving options, but none of these worked. Any reply would be much appreciated. Thanks.

Level 9
I am not sure how well a Corsair H55 would cool a 4790K even at optimized defaults. One other note, memory speed would also come into play on the temps.

What are you referring to when you say you think it may be CPU Speed and voltage? Are you trying to overclock?
Can you post images of your bios settings?

Level 12
I would also question the H55 cooling performance for a 4790K, even at stock speeds.
Run CPU-Z or HWMonitor to monitor your CPU voltage when running a stress program.
800MHz idle is normal, don't think I've ever seen my 4790K go below that frequency.

I would also suggest running ROG RealBench stress test and see how your temps look with this program under load.
Intel i9 10850K@ 5.3GHz
ASUS ROG Strix Z490-E
Corsair H115i Pro XT
G.Skill TridentZ@ 3600MHz CL14 2x16GB
EVGA RTX 3090 Ti FWT3 Ultra
OS: WD Black SN850 1TB NVMe M.2
Storage: WD Blue SN550 2TB NVMe M.2
EVGA SuperNova 1200 P2
ASUS ROG Strix Helios GX601

I'll what you said and post some screenshots later. Thanks.

Level 7
Well everything was working fine until a few days ago, I changed the system settings in EZ Mode of BIOS to ASUS Optimal mode, which somehow automatically increased my CPU's Vcore. Beforehand, I was able to get 60-70ºC on Prime95 and my CPU idled at around 100MHz. Now it BOOTS at 4GHz, then slows back down, which is weird. Do any of you know why this is happening?