The reference provided by nkurz measured clearly that it is a net win in most cases.  However, that fact isn&#x27;t inherantly obvious.  CPU&#x27;s aggressively use clock gating to shut down idle parts of the processor at a fine-grained level.  So avoiding the use of several entire compute units does have some savings as well.  The difference is that I was assuming something more like 2x power usage, where the actual difference is in the small single digits.