Energy efficient asymmetrically ported register files

Abstract

Power consumption in the register file (RF) forms a considerable fraction of the total power consumption in a chip. With increasing instruction window sizes and issue widths, RF power consumption will suffer a significantly large growth. Using the fact that many of the register values are small and require only a small number of bits for representation, we propose a novel asymmetrically ported RF (to reduce RF power consumption), in which some of the ports can only read/write small-sized values. We experiment with both monolithic and partitioned versions of asymmetrically ported RFs. The power savings in the RF with partitioned asymmetrically ported RF reach as high as 60%. These reductions in RF power consumption come with about 40% improvement in RF access-time and a negligible impact on IPC (instructions per cycle).