AVICA: An Access-time Variation Insensitive L1 Cache Architecture

Abstract

Ever scaling process technology increases variations in transistors. The process variations cause large fluctuations in the access times of SRAM cells. Caches made of those SRAM cells cannot be accessed within the target clock cycle time, which reduces yield of processors. To combat these access time failures in caches, many schemes have been proposed, which are, however, limited in their coverage and do not scale well at high failure rates. We propose a new L1 cache architecture (AVICA) employing asymmetric pipelining and pseudo multi-banking. Asymmetric pipelining eliminates all access time failures in L1 caches. Pseudo multi-banking minimizes the performance impact of asymmetric pipelining. For further performance improvement, architectural techniques are proposed. Our experimental results show that our proposed L1 cache architecture incurs less than 1% performance hit compared to the conventional cache architecture with no access time failure. Our proposed architecture is not sensitive to access time failure rates and has low overheads compared to the previously proposed competitive schemes.