how are you switching? close the bsd, or just change the bios rom and reset and go?
I'm not totally inclined to totally trust the sim depending on how you are doing the switch. The sim seems to like reset between switching bios flash parts. My procedure is to have a coreboot bsd, and always close and open that bsd when I change things; and, finally, once the bsd opens, I always hit reset.
I start with a break at fffffff0 to make doubly sure I started up ok.
ron