I see, interesting. Definitely sounds like a kernel thing, and I honestly wonder if it isn't a BIOS/firmware issue with the Nvidia GPU handling incomplete initialization sanely. I wonder what would happen if you just tried booting DOS or some other OS on the thing. Or just sat in the BIOS?

If booting into something barebones leaves everything cool, and depending on how long it takes for the chip to get warm, perhaps you could move a `for (;;);` further and further down into the OpenBSD kernel and find the point things get cranky that way.

Extremely hacky approach though, I'll definitely concede that point >.>

(But if you want to try it, I would wholeheartedly recommend looking into something like iPXE, which would let you download each test kernel over HTTP at boot time and make the iteration process tolerable. This assumes you have a second machine though...)