ReadDuo: Constructing Reliable MLC Phase Change Memory through Fast and Robust Readout

Abstract

Phase change memory (PCM) has emerged as a promising non-volatile memory technology. Multi-level cell (MLC) PCM, while effectively reducing per bit fabrication cost, suffers from resistance drift based soft errors. It is challenging to construct reliable MLC chips that achieve high performance, high storage density, and low energy consumption simultaneously. In this paper, we propose ReadDuo, a fast and robust readout solution to address resistance drift in MLC PCM. We first integrate fast current sensing and resistance drift resilient voltage sensing, which exposes performance optimization opportunities without sacrificing reliability. We then devise last writes tracking and selective different write schemes to minimize performance and energy consumption overhead in scrubbing. Our experimental results show that ReadDuo achieves 37% improvement on average over existing solutions when considering performance, dynamic energy consumption, and storage density all together.