Or would the shadowing be oneshot before the new biosloader runs?
The registers have to be changed _after_ bios.bin is copied to the E and F segment.
Doh. Yes. Oneshot _in_ the new biosloader, before bios.bin runs.
Should bios.bin run in x86emu or vm86 by the way?
No x86emu here. Otherwise your OS will start up in x86emu, too... Might be an option for Carl-Daniel's upcoming MIPS port. ;-)