 The entropy of a NOP slide is dependent upon the constraints placed on it.If it can be determined that certain registers are not in use (that is to say, they will be set to a known value before their next use), instructions which manipulate them arbitrarily may be used in the NOP slide.Additionally, if the alignment of both the NOP slide and the instruction pointer are deterministic, multi-byte instructions can be used in a NOP slide without regard to the results of unaligned execution.