Okay, I couldn't wait for Hicookie to return from his biz trip, so did some quick reverse engineering. Here's the modification for the GA-H55M-UD2H and the socket pin it's connected to. Normally, the resistance of this pin is ~ 750ohm. Connect to GND means it'll be 0ohm. Just trace back to resistor and remove the resistor and connect both points, or just solder over the resistor. Should actually work on any board ... but I'm not responsible if this turns out incorrect.
Anyway, just did the mod and I can boot up at -130°C no problem now. Same 661 as I'm using with the Trinergy.
Works for me, but if you're not comfortable trying this out yourself wait for Hicookie's confirmation!