The computational complexity of a probability-based combinational power metric lies in the creation of a BDD for each node in the circuit. In this paper, we formalize the problem of finding intermediate support-set which controls the size of BDD. We propose an exact algorithm to solve it. We also propose an heuristic solution, PowerDrive, for estimating power of large circuits. Apart from being more accurate and several times faster than [2, 7] , PowerDrive possess the unique quality of being

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... nonical and of constant complexity, a very desirable quality for a power metric guiding a synthesis tool. Finally, the proposed power metric was able to guide the synthesis tool [11] to optimize large circuits which could not be synthesized by POSE [6], thus proving the effectiveness of our power metric.