I don't really think there is a need for an "alternative" NOP, because the XCHG side effect (of clobbering the TMP register) is of little practical concern. In

I don't really think there is a need for an "alternative" NOP, because the XCHG side effect (of clobbering the TMP register) is of little practical concern. In fact, as far as I have been able to determine, the malformed JMP/CALL FAR m32 operation -- which isn't even remotely useful! -- is the only way that code is even able to 'observe' the TMP register in the first place. For all practical purposes 90h is indeed a NOP, despite the fact that the CPU actually executes the opcode.