Enhancing Performance and Energy Consumption of HER Caches by Adding Associativity

Abstract

Abstract. Unlike other previous techniques, the recently proposed Hard Error Recovery (HER) fault-tolerant cache provides 100% fault-coverage in L1 data caches. This full coverage makes the HER cache appropiate for fault-dominated future technology nodes. An n-way set-associative HER cache implements one cache way with fast SRAM banks and the remaining ways with eDRAM banks to address power and area. Since the number of eDRAM cache blocks used in a specific HER cache organization depends on the cache associativity (i.e., the implemented number of ways), we expect that the performance and energy consumption provided by a given HER cache design strongly depends on the cache geometry. In this work we study the behavior of the HER cache design when applied to a highly associative L1 cache like those found in some modern microprocessors. In particular this work explores a 32KB 8-way associative L1 data cache such as the one used in Intel Haswell microarchitecture. Experimental results show that, at low-power modes compared to a conventional cache with the same storage capacity and number of ways, area, leakage power, and dynamic energy savings of a 4-way HER cache are by 25%, 85%, and 62%, respectively. These percentages are further improved (by 40%, 89%, and 68%, respectively) when the cache associativity is increased to 8 ways, while the performance loss with respect to both an 8-way conventional cache and the 4-way HER cache is minimal.