i7-8700K [edit: delidded]
5.0 GHz all cores
-2 AVX offset
LLC level 5
manual 1.42v
both CPU package power limits set to 200W
originally using "extreme" VRM power phase control and duty cycle, but throttling persists on standard/t.probe mode as well

So far I have only seen the throttling occur under Linpack AVX stress.

All the temps I can read in the ASUS software or HWiNFO look fine: https://i.imgur.com/YdQVRTU.png

Is there no API to read the VRM temps? I don't see them anywhere, at least not labeled as such.

I'm using a Corsair h80i-v2 in a Phanteks Shift case. There's a 140mm fan right at the edge of the motherboard blowing onto it.