Datapath scheduling with multiple supply voltages and level converters

We present an algorithm called MOVER (Multiple Operating Voltage Energy Reduction) to minimize datapath energy dissipation through use of multiple supply voltages. In a single voltage design, the critical path length, clock period, and number of control steps limit minimization of voltage and power. Multiple supply voltages permit localized voltage reductions to take up remaining schedule slack. MOVER initially finds one minimum voltage for an entire datapath. It then determines a second voltage for operations where there is still schedule slack. New voltages con be introduced and minimized until no schedule slack remains. MOVER was exercised for a variety of DSP datapath examples. Energy savings ranged from 0% to 50% when comparing dual to single voltage results. The benefit of going from two to three voltages never exceeded 15%. Power supply costs are not reflected in these savings, but a simple analysis shows that energy savings can be achieved even with relatively inefficient DC-DC converters. Datapath resource requirements were found to vary greatly with respect to number of supplies. Area penalties ranged from 0% to 170%. Implications of multiple voltage design for IC layout and power supply requirements are discussed.