Cache Leakage Reduction Techniques for Hybrid SPM-Cache Architectures

Abstract

Leakage energy has become an increasingly large fraction of total energy consumption, making it important to reduce leakage energy for improving the overall energy efficiency for embedded processors. In this paper, we explore how to reduce the cache leakage energy efficiently in a hybrid Scratch-Pad Memory (SPM) and cache architecture. Different from stand-alone cache, since the frequently used data may be allocated to the SPM for rapid retrieval in the hybrid architecture, the access frequency to the cache is reduced. It is possible to place the cache lines of the hybrid SPM-cache into the low power mode more aggressively than traditional leakage management for regular caches, which can reduce more leakage energy without significant performance degradation. Also, we propose a Hybrid Drowsy-Gated VDD (HDG) technique, which can adaptively exploit both short and long idle intervals of cache accesses to minimize leakage energy with insignificant performance overhead. In addition, we discussed the impact of cache size on the idle intervals of accesses, which will affect the efficiency of leakage management methods that exploit the idle intervals to reduce leakage energy.