Value-conscious cache: simple technique for reducing cache access power

Most microprocessors employ the on-chip caches to bridge the performance gap between the processor and main memory. However, the cache accesses usually contribute significantly to the total power consumption of the chip. Based on the observation that an overwhelming majority of the cache access bits are ´0´, in this paper we propose a value-conscious (VC) cache to reduce the average cache power consumption during an access. Unlike the conventional cache with differential-bitline implementation, the VC cache is a single-bitline design. Depending on the access bit value, the VC cache can dynamically prevent the bitline from being discharged such that the power dissipated in accessing ´0´ is much less than the power dissipated in accessing ´1´. The implementation of the VC cache is a circuit-level technique, which is software independent and orthogonal to other low power techniques at architecture-level. The experimental results based on the SPEC2000 and MediaBench traces show that without compromise of both performance and stability, by exploiting the prevalence of ´0´ bits in access data the VC cache can reduce the average cache read and write power by about 18%∼22% and 36%∼40%, respectively.