Energy/Power Breakdown of Pipelined Nanometer Caches (90nm/65nm/45nm/32nm)

Abstract

As transistors continue to scale down into the nanometer regime, device leakage currents are becoming the dominant cause of power dissipation in nanometer caches, making it essential to model these leakage effects properly. Moreover, typical microprocessor caches are pipelined to keep up with the speed of the processor, and the effects of pipelining overhead need to be properly accounted for. In this paper, we present a detailed study of pipelined nanometer caches with detailed energy/power dissipation breakdowns showing where and how the power is dissipated within a nanometer cache. We explore a three-dimensional pipelined cache design space that includes cache size (16kB to 512kB), cache associativity (direct-mapped to 16-way) and process technology (90nm, 65nm, 45nm and 32nm). Among our findings, we show that cache bitline leakage is increasingly becoming the dominant cause of power dissipation in nanometer technology nodes. We show that subthreshold leakage is the main cause of static power dissipation, and that gate leakage is, surprisingly, not a significant contributor to total cache power, even for 32nm caches. We also show that accounting for cache pipelining overhead is necessary, as power dissipated by the pipeline elements is a significant part of cache power