Drift-tolerant Coding to Enhance the Energy Efficiency of Multi-Level-Cell Phase-Change Memory

BSTRACTPhase-Change Memory (PCM) has emerged as a promising memory and storage technology in recent years, and Multi-Level-Cell (MLC) PCM further reduces the per-bit cost to improve its competitiveness by storing multiple bits in each PCM cell. However, MLC PCM has high energy consumption issue in its write operations. In contrast to existing works that try to enhance the energy efficiency of the physical program&verify strategy for MLC PCM, this work proposes a drift-tolerant coding scheme to enable the fast write operation on MLC PCM without sacrificing any data accuracy. By exploiting the resistance drift and asymmetric write characteristic of PCM cells, the proposed scheme can reduce the write energy consumption of MLC PCM significantly. Meanwhile, a segmentation strategy is proposed to further improve the write performance with our coding scheme. A series of analyses and experiments was conducted to evaluate the capability of the proposed scheme. The results show that the proposed scheme can reduce 6.2–17.1% energy consumption and 3.2–11.3% write latency under six representative benchmarks, compared with the existing well-known schemes.