Random aggressive CPU throttling while under load? (not thermal)

[Mince]

Recently while playing CSGO and other games I've noticed some very very aggressive throttling on my 6700k, dropping from 4.0 GHz to 0.8GHz (Which results in massive frame drops)

I read online that this happens when the CPU isn't under load and windows reduces it's clock speed to save on power and this is normally solved by just setting the power plan to high performance mode. However, I did and it's still happening

Another possibility is that the VRM is overheating but I read that those can go up to 125C without throttling which they seem to be well below

 

Could it be my PSU? I have a Corsair SF600, I imagine that's plenty enough for a 6700k and 1080? Otherwise I have no clue what could be causing it. This hasn't happened for the past 3 or so years, and only happened upon using a hard drive as opposed to an SSD since my windows instillation got messed up on my SSD and I'm backing up files. 

[AkSo2504]

Post your complete system specs please.

You can try to update your bios, maybe it will help.