Thor: Thermal-aware optimizations for extending reram lifetime

Resistive RAM (ReRAM) is an emerging memory technology that has been proposed as a promising alternative for DRAM-based main memory. In addition to being more scalable and non-volatile, ReRAM also has the capability of performing logic functions. In this paper, we aim to investigate using 3D stacked ReRAM to achieve a scalable and high-performance memory system architecture. 3D integration of ReRAM crossbar layers (i.e., 3D crossbar) is a potential method for further improving ReRAM density. However, 3D architectures typically suffer from high operating temperatures, which adversely impact ReRAM reliability and device performance. The objective of this study is to address ReRAM endurance limitations, which is a major drawback for such resistive memory technologies. Specifically, we analyze the impact of temperature on ReRAM endurance in 3D and 2.5D stacking designs and show that stacking ReRAM onto multicore dies (i.e., 3D stacking design) may cause lifetime concerns. We then propose a novel solution to improve the access efficiency and reduce the number of accesses to the overheated ReRAM banks. The goal of our mechanism which is mainly utilized for the 2.5D design, is to perform slower and fewer accesses to hot banks to cool them. Evaluation results show that our technique called THOR, can achieve 2.06× lifetime enhancement and 7.5°C peak temperature reduction over a baseline design with only 1.9% performance degradation while running on the 2.5D design.