Mitigating Write Disturbance Errors of Phase-Change Memory as In-Module Approach

With the growing demand for technology scaling and storage capacity in server systems to support high-performance computing, phase-change memory (PCM) has garnered attention as the next-generation non-volatile memory to satisfy these requirements. However, write disturbance error (WDE) appears as a serious reliability problem preventing PCM from general commercialization. WDE occurs on the neighboring cells of a written cell due to heat dissipation. Previous studies for the prevention of WDEs are based on the write cache or verify-n-correction while they often suffer from significant area overhead and performance degradation, making it unsuitable for high-performance computing. Therefore, an on-demand correction is required to minimize the performance overhead. In this paper, an in-module disturbance barrier (IMDB) mitigating WDEs is proposed. IMDB includes two sets of SRAMs into two levels and evicts entries with a policy that leverages the characteristics of WDE. In this work, the comparator dedicated to the replacement policy requires significant hardware resources and latency. Thus, an approximate comparator is designed to reduce the area and latency considerably. Furthermore, the exploration of architecture parameters is conducted to obtain cost-effective design. The proposed work significantly reduces WDEs without a noticeable speed degradation and additional energy consumption compared to previous methods.