Retention-Aware Hybrid Main Memory (RAHMM): Big DRAM and Little SCM

Abstract

Hybrid memory comprised of a big SCM and a little DRAM (BSLD) is widely studied to address the growing power consumption challenge of pure DRAM. However, the performance degradation, limited endurance and immature mass production of ultra-high-density SCM are still the painful points of BSLD. Here we propose a Retention-Aware Hybrid Main Memory (RAHMM) architecture with a big DRAM and a little SCM (BDLS) for the first time. DRAM is refreshed at a much longer interval by using SCM to store the small quantity of leaky tail bits in DRAM. A two-step search technology combined with outcome forecasting is put forward to get ultra-fast read access, as well as to diminish the power and performance overheads. A hidden buffer strategy (HBS) is proposed to optimize write performance and endurance hurt. The experimental results show 45 percent reduction of power consumption and 30 percent performance optimization, which are significantly improved compared to that of both serial and parallel BSLD with a counterpart capacity