R&D: Towards Write Optimization for Skyrmion Racetrack Memory by Skyrmion Re-Permutation

IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems has published an article written by Tsun-Yu Yang, Xiangjun Peng, Shatin, The Chinese University of Hong Kong, Department of Computer Science and Engineering, Hong Kong, Wang Kang, School of Integrated Circuit Science and Engineering, Beihang University, Beijing, China, and Ming-Chang Yang, Shatin, The Chinese University of Hong Kong, Department of Computer Science and Engineering, Hong Kong.

Abstract: “Skyrmion racetrack memory (Sky-RM), as an emerging non-volatile memory technology, provides both high-density data storage and low-access latency, accompanying with a novel feature of using current to shift data along a racetrack. However, it is time-comsuing and energy-hungry to write/inject new particle-like Skyrimons on Sky-RM compared with other manipulations. Thus, the goal of this work is to presents a novel strategy to optimize write performance in Sky-RM, Permutation-Write (PW). Particuarly, PW reduces the number of Skyrmion injections when writing data, by “re-permuting” existing Skyrmion particles within a racetrack. Moreover, based on the flexible concept of re-permutation, this work further proposes PW+ strategy, which is an optimized PW strategy integrated with injection and shift optimizations to achieve better performance. Our evaluation results justify that PW+ can greatly reduce the amount of Skyrmion injections, which are considered highly expensive in Sky-RM, by at least 50%, compared with other state-of-the-art write-optimized strategies. Furthermore, PW+ only incurs 1.79 injections, averaged for every 64-bit-word write. We show that PW+ strategy can bring significant benefits over other state-of-the-art write-optimized strategies by about 16-50% for every 64-bit-word write, for both performance and energy efficiency.“