Reconditioning: Automatic Power Optimization of QDI Circuits

This paper introduces reconditioning: a novel systematic technique for reducing unnecessary switching activity of asynchronous gate-level net lists, which involves the optimal reordering of conditional communication and logic primitives. Our technique is applicable to asynchronous circuits with handshaking protocols that encode data and control together, in particular, QDI and 1-of-N handshaking circuits. Both an optimal integer linear program (ILP) and a fast heuristic algorithm are presented. We show that our ILP is feasible for moderate size circuits and our heuristic algorithm scales to much larger circuits, completing in seconds on circuits with tens of thousands of gates. Our experimental results shows power improvement highly depends on the structure of the circuit but can often be above 40% with typically less than 5% area overhead.