C1C

Abstract

Spin-Transfer Torque RAM (STT-RAM), a promising alternative to SRAM for reducing leakage power consumption, has been widely studied to mitigate the impact of its asymmetrically long write latency. Recently, STT-RAM has been proposed for L1 caches by relaxing the data retention time to improve write performance and dynamic energy. However, as the technology scales down from 65nm to 22nm, the performance of the read operation scales poorly due to reduced sense margins and sense amplifier delays. In this article, we leverage a dual-mode STT memory cell to design a configurable L1 cache architecture termed C1C to mitigate read performance barriers with technology scaling. Guided by application access characteristics discovered through novel compiler analyses, the proposed cache adaptively switches between a high performance and a low-power access mode. Our evaluation demonstrates that the proposed cache with compiler guidance outperforms a state-of-the-art STT-RAM cache design by 9% with high dynamic energy efficiency, leading to significant performance/watt improvements over several competing approaches.