r/m16 -> Sreg
Sreg -> r/m16
movw copies the first operand to the second operand, including data from a descriptor. The descriptor table entry for the selector contains the data for the register. The DS and ES registers can be loaded with a null selector without causing an exception. Use of DS or ES however, causes a #GP(0), and no memory reference occurs.
All interrupts are inhibited until after the execution of the next instruction, after a movw into SS. Special actions and checks result from loading a segment register under Protected Mode.
movw %CS, 5(%ebx) movw %(%ebx), %CS