mov bx，ax和mov bh之间的速度是否存在差异啊？

Question

在用于8086架构的16位MS-DOS应用程序中， mov bx,ax和mov bh,ah之间的速度是否存在差异？

Answer 1

You don't specify the architecture, but at least in 8086 , 286 , 386 and 486 they execute in the same number of clocks: 2 clocks in 8088/8086 , 286 and 386 for either instruction, 1 clock in 486 for either instruction. See link .

Answer 2

If in doubt, profile. But it's very unlikely in this case. From what I gleaned from the Intel 64 and IA32 Architectures Optimization Reference Manual it appears to be that they both perform identically but usually slower than their 32-bit or 64-bit counterparts.