Continuous On-Chip Learning in Neural Networks using SOT-MRAM based CIM Architectures

Abstract

Computational-In-Memory (CIM) is an energy-efficient paradigm that integrates computation directly within memory arrays, reducing the bottleneck associated with data transfer. This approach is beneficial for Artificial Intelligence (AI) applications that require on-chip learning for real-time processing. However, implementing on-chip learning in CIM architectures remains challenging due to limited throughput and energy-efficiency during both online training and inference. In conventional architectures, weight updates necessitate the inference process to halt to avoid unintended computation outcomes. To overcome this limitation, this paper presents a novel Spin-Orbit Torque (SOT)-based CIM architecture tailored for continuous on-chip learning applications, which enable weight updates without interrupting the inference. The proposed SOT bit-cell utilizes two read ports and one write port (2R1W) configuration, where one read port (1R) is dedicated to inference and one read and one write (1R1W) for on-chip learning that enables concurrent read and write operations. Our proposed architecture is evaluated at the system-level using the Generic-PDK 45 nm technology node, demonstrating 2.4× improvement in energy-efficiency and 5.4× improvement in throughput compared to state-of-the-art solutions, with minimal overhead.