Joint Write Policy and Fault-Tolerance Mechanism Selection for Caches in DSM Technologies: Energy-Reliability Trade-off

Mehrtash Manoochehri, Alireza Ejlali, Seyed Ghassem Miremadi
Department of Computer Engineering, Sharif University of Technology


Write-through caches potentially have higher reliability than write-back caches because all data of write-through caches exist in the next memory level. However, the energy consumption of write-through caches is higher because of more accesses to the next memory level. This paper provides a comparison between the write-back and write-through policies based on the combination of reliability and energy consumption criteria. In this comparison, different feature sizes and different L1 and L2 cache sizes are considered. In the experiments, SIMPLESCALAR tool and CACTI model are used to evaluate the characteristics of the caches. The results show that a write-through cache with one parity bit per word is as reliable as a write-back cache with SEC-DED code per word. Furthermore, the results show that the energy saving of the write-through cache over the write-back cache increases if any of the following changes happens: i) a decrease in the feature size, ii) a decrease in the L2 cache size, and iii) an increase in the L1 cache size. The results also show that when feature size is bigger than 32nm, the write-back cache is usually more energy efficient. However, for 32nm and smaller feature sizes the write-through cache can be more energy efficient.