Design Flow for Flip-Flop Grouping in Data-Driven Clock Gating

Abstract — Clock gating is a predominant technique used for power saving. It is observed that the commonly used synthesis-based gating still leaves a large amount of redundant clock pulses. Data-driven gating aims to disable these. To reduce the hardware overhead involved, flip-flops (FFs) are grouped so that they share a common clock enabling signal. The question of what is the group size maximizing the power savings is answered in a previous paper. Here we answer the question of which FFs should be placed in a group to maximize the power reduction. We propose a practical solution based on the toggling activity cor-relations of FFs and their physical position proximity constraints in the layout. Our data-driven clock gating is integrated into an Electronic Design Automation (EDA) commercial backend design flow, achieving total power reduction of 15%–20 % for various types of large-scale state-of-the-art industrial and academic designs in 40 and 65 manometer process technologies. These savings are achieved on top of the savings obtained by clock gating synthesis performed by commercial EDA tools, and gating manually inserted into the register transfer level design. Index Terms — Clock gating, clock networks, dynamic power reduction. I