AdaMS: Adaptive MLC/SLC phase-change memory design for file storage

Phase-change memory (PCM) is an emerging memory technology that has made rapid progress in the recent years, and surpasses other technologies such as FeRAM and MRAM in terms of scalability. Recently, the feasibility of multi-level cell (MLC) for PCM, which enables a cell to store more than one bit of digital data, has also been shown. This new property makes PCM more competitive and considered as the successor of the NAND flash technology, which also has the MLC capability but does not have an easy scaling path to reach higher densities. However, the MLC capability of PCM comes with the penalty of longer programming time and shortened cell lifetime compared to its single-level cell (SLC) mode. Therefore, it suggests an adaptive MLC/SLC reconfigurable PCM design that can exploit the fast SLC access speed and the large MLC capacity with the awareness of workload characteristics and lifetime requirements. In this work, a circuit-level adaptive MLC/SLC PCM array is designed at first, the management policy of MLC/SLC mode is proposed, and finally the performance and lifetime of a novel PCM-based SSD with run-time MLC/SLC reconfiguration ability is evaluated.