Performance and Power Optimizations for Highly Reliable Caches




Azizabadifarahani, Seyedmostafa

Journal Title

Journal ISSN

Volume Title



This thesis introduces performance and power optimization techniques for caches. Our optimization techniques target both conventional caches, which are implemented using six-transistor (6T) cells, and highly reliable caches implemented using eight-transistor (8T) cells. In 6T cell caches, we enhance leakage power dissipation by adapting a previous proposed technique, Drowsy Cache, according to the application behavior. We show that spatial locality in embedded applications is low and Drowsy Cache misses a significant leakage power saving opportunities. By taking a finer granularity approach, we achieve a significant leakage power reduction with minimal performance overhead. Although 6T cell caches are commonly used, we show that they are not proper choice for future designs due to poor stability. We investigate 8T cells as alternative reliable designs for implementing caches. However, Column Selection Issue limits efficiency of 8T cells during write operations. Previous solution, Read-Modify-Write (RMW), addressed column selection issue by requiring a read operation before each write operation, imposing significant overhead on performance, cache traffic, and power. We observe that a significant share of cache accesses in RMW is either redundant or unnecessary, consequently can be avoided without compromising program execution consistency. Based on our observations, we propose two techniques which exploit a buffering mechanism to detect and filter out unnecessary and redundant cache accesses. Our simulation results show that our techniques improve performance and cache traffic effectively in 8T cell caches. Furthermore, we propose a novel dual threshold 8T cell which reduces leakage power significantly with negligible impact on performance. Our proposed cell also improves stability and robustness to process variations compared to the conventional 8T cells.



dynamic power, leakage power, reliability, 8T cells, column selection issue, cache