AH is no more of an anachronism in 64-bit code than it was in 32-bit code; AL, AH, AX, EAX, RAX; all bit slices of the same register. The addition of RAX doesn'

AH is no more of an anachronism in 64-bit code than it was in 32-bit code; AL, AH, AX, EAX, RAX; all bit slices of the same register. The addition of RAX doesn't change the fact that AH is still a bit weird (it's the only one that doesn't include the low bits of the total register).