Energy-efficient multi-level cell phase-change memory system with data encoding

Phase-change memory (PCM) is one of the most promising technologies among emerging non-volatile memories. Recently, the technology of multi-level cell (MLC) for PCM has been developed and a high capacity memory system can be implemented by storing multiple bits in a cell. However, programming MLC PCM involves the program-and-verify scheme. Thus, the energy of programming intermediate states in MLC PCM is considerably larger than that of single-level cell (SLC) PCM. To mitigate the MLC energy overhead, we propose an energy-efficient PCM architecture using data encoding write based on the observation that there are significant value-dependent energy variations in programming MLC PCM. In addition, data comparison write (DCW) is adopted to enhance the effectiveness of the proposed data encoding architecture for MLC PCM. Simulation results show that this encoding architecture achieves 9.6% average energy saving (up to 19.8%) on the plain MLC PCM system, and 12.9% average energy saving (up to 26.7%) on the DCW-adopted MLC PCM system.