Booting into the BIOS usually means there is a problem that needs to be fixed. If the BIOS lets you save and quit, and then it boots, the situation is not dire but you seem to be getting a restart/BSOD, so something is not right.

Do you have specific voltage settings for the CPU? Not all on Auto? You should go through the CPU and memory BIOS settings and see if something is not right for the new CPU, or set the settings to Auto is they aren't now, to see if that clears it up.

BIOS 2.20 not being compatible with your board makes no sense, not saying you're doing something wrong. I've always wondered in the Chipset/INF installation program should be run again when changing CPUs. That is supposed to only be for the chipset features, but who knows...