At high-level synthesis for system VLSIs, their power consumption is efficiently reduced by applying gated clocks to them. Since using gated clocks causes the reduction of power consumption and the increase of area/delay, estimating trade-off between power and area/delay by applying gated clocks is very important. In this paper, we discuss the amount of variance of area, delay and power by applying gated clocks. We propose a simple gate-level circuit model and estimation equations. We vary parameters in our proposed circuit model, and evaluate power consumption by back-annotating gate-level simulation results to the original circuit. This paper also proposes a conditional expression for applying gated clocks. The expression shows whether or not we can reduce power consumption by applying gated clocks. We confirm the accuracy of proposed estimation equations by experiments.

This paper proposes a high-level energy-optimizing algorithm which can synthesize low energy system VLSIs. Given an initial system hardware obtained from an abstract behavioral description, the proposed algorithm applies to it the three energy reduction techniques, 1) reducing supply voltage, 2) selecting lower energy modules, and 3) applying gated clocks. By incorporating our area/delay/power estimation, the proposed algorithm can obtain low energy system VLSIs meeting the constraints of area, delay, and execution time. The proposed algorithm has been incorporated into a high-level synthesis system and experimental results demonstrate effectiveness and efficiency of the algorithm.