Improving reliability, performance, and energy efficiency of STT-MRAM with dynamic write latency

Abstract

High write latency and high write energy are the major challenges in Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) design. The write operation in STT-MRAM is of stochastic nature. Therefore, it requires a very long timing margin to maintain an acceptable level of reliability and yield. Traditionally, Error Correction Codes (ECCs) are used to reduce the timing margin in STT-MRAM. However, they impose high storage and latency overheads. In this paper, we propose a low-cost architecture-level technique to significantly reduce the amount of required timing margin. This technique employs a handshaking protocol between the memory and its controller to dynamically determine the write latency at run-time. Our simulation infrastructure comprehensively models the combined effect of process variation and stochastic write behavior at circuit-level and abstracts it to architecture-level. The simulation results show that the proposed technique not only considerably reduces the write error rate but also improves the overall system performance on average by 15.4% compared to existing solutions.