Probably not a lot, I did a V6 port in the early 80s, from memory porting the compiler was most of the work, V6 was probably a couple of months. The MMU is easy

Probably not a lot, I did a V6 port in the early 80s, from memory porting the compiler was most of the work, V6 was probably a couple of months. The MMU is easy, it's a swapping port, the only real weirdness is the context switch which assumes a lot about what the compiler is doing, v7 got that much more right