Practical considerations of clock-powered logic

Recovering and reusing circuit energies that would otherwise be dissipated as heat can reduce the power dissipated by a VLSI chip. To accomplish this requires a power source that can efficiently inject and extract energy, and an efficient power delivery system to connect the power source to the circuit nodes. The additional circuitry and timing required to support this process can readily exceed the power-savings benefit. Clock-powered logic is a circuit-level, energy-recovery approach that has been implemented in two generations of small-scale microprocessor experiments. The results have shown that it is possible and practical to extract useful amounts of power savings by leveraging the additional circuitry for other compatible purposes. The capabilities and limitations of clock-powered logic as a competitive low-power approach are presented and discussed in this paper.