A Study on Performance and Power Efficiency of Dense Non-Volatile Caches in Multi-Core Systems

This paper presents a novel cache design based on Multi-Level Cell Spin-Transfer Torque RAM (MLC STT-RAM).Our design exploits the asymmetric nature of the MLC STT-RAM to build cache lines featuring heterogeneous performances, that is, half of the cache lines are read-friendly,while the other half are write-friendly--this asymmetry in read/write latencies are then used by a migration policy in order to overcome the high latency of the baseline MLC cache. Furthermore, in order to enhance the device lifetime, we propose to dynamically deactivate ways of a set in underutilized sets to convert MLC to Single-Level Cell (SLC)mode.Our experiments show that our design gives an average improvement of 12% in system performance and 26% in last-level cache(L3) access energy for various workloads.