WoM-SET: Low power proactive-SET-based PCM write using WoM code

Abstract

The emerging Phase Change Memory (PCM), while having many advantages, suffers from slow write operations. This is mainly due to its asymmetric write characteristic, i.e., for two types of write operations of PCM, SET is much slower than RESET. Recent study has shown that proactively setting dirty memory lines to all ‘1’s can enable RESET-only writes when these lines are written back from the cache, which helps to reduce the effective write latency. Unfortunately, it results in higher write power demand. In this paper, we propose WoM-SET, a low power proactive-SET-based write strategy. By exploiting the WoM (write-once memory) code, we greatly reduce the number of RESETs per write and hence the write power demand. By applying our design only to write-intensive pages, we restrict the extra space requirement in WoM-SET. Our experiments show that WoM-SET achieves 40% RESET bit reduction, 40% write power reduction, and 12% energy-delay-product improvement over the PreSET scheme.