OH MAYBE THIS IS WHY
this is not how 3 pin fan connectors work! This is going to try to undervolt your fan backwards while putting +12v down the tach-out pin

amazingly it turns out I didn't fry my fan. after adapting to the Weird Pinout here, it works fine.

well, relatively "works fine". the fan spins.
I still haven't managed to get this computer to respond to any keyboards and when I boot it, it's started looking like this:

@foone Hit F1!

@rperez I WAS TRYING, but I have no keyboard yet!