> A 32-bit assembler (like gas) will turn `mov %esp,%ebp` into `89 e5` while `mov %sp,%bp` becomes `66 89 e5` -- the former being correct when actually in 16-bi

> A 32-bit assembler (like gas) will turn `mov %esp,%ebp` into `89 e5` while `mov %sp,%bp` becomes `66 89 e5` -- the former being correct when actually in 16-bit. He is using nasm with "bits 16" directive, so 66 prefix will be emitted for "mov ebp,esp". gas with 32-bit target is totally unrelated to this discussion. > http://wiki.osdev.org/Unreal_Mode http://wiki.osdev.org/Unreal_Mode So what? MBR runs in 16-bit real mode.