Synthesis of resonant clock networks supporting dynamic voltage / frequency scaling

Abstract

The portion of clock power in system is rapidly increasing with the continuous increasing of clock frequency and clock resources. Last two decades, a great research attention has been paid to minimizing the clock power. Recently, it is shown that the structure of resonant clock networks is very effective in saving power since it can store electric energy to the inserted inductors rather than dissipate. On the other side, it has been known that dynamic voltage-frequency scaling (DVFS) is one of the most effectively and widely used power reduction techniques. However, so far no works have addressed the problem of synthesizing resonant clock networks that are able to operate under the designs with DVFS capability even though the problem is potentially very important to maximize the synergy effect on saving power. In this context, this work proposes a comprehensive solution to the problem. Precisely, we propose a two-phase synthesis algorithm: (1) formulating the problem of inductor allocation, placement, and adjustable-sizing to support DVFS into a weighted set cover problem with the objective of minimizing total area of inductors followed by (2) performing the task of resizing of adjustable driving buffers to support the switch of driving strength according to the clock frequencies by DVFS. Through experiments with benchmark circuits, it is shown that for designs with DVFS using 1GHz and 3GHz, our algorithm synthesizes resonant clock networks with 17% less power on the execution of the clock frequency, which is not supported by resonant clocking in the previous no-DVFS aware resonant clock synthesis algorithm.