AERIS - area/energy-efficient 1T2R ReRAM based processing-in-memory neural network system-on-a-chip.

ReRAM-based processing-in-memory (PIM) architecture is a promising solution for deep neural networks (NN), due to its high energy efficiency and small footprint. However, traditional PIM architecture has to use a separate crossbar array to store either positive or negative (P/N) weights, which limits both energy efficiency and area efficiency. Even worse, imbalance running time of different layers and idle ADCs/DACs even lower down the whole system efficiency. This paper proposes AERIS, an Area/Energy-efficient 1T2R ReRAM based processing-In-memory NN System-on-a-chip to enhance both energy and area efficiency. We propose an area-efficient 1T2R ReRAM structure to represent both P/N weights in a single array, and a reference current cancelling scheme (RCS) is also presented for better accuracy. Moreover, a layer-balance scheduling strategy, as well as the power gating technique for interface circuits, such as ADCs/DACs, is adopted for higher energy efficiency. Experiment results show that compared with state-of-the-art ReRAM-based architectures, AERIS achieves 8.5x/1.3x peak energy/area efficiency improvements in total, due to layer-balance scheduling for different layers, power gating of interface circuits, and 1T2R ReRAM circuits. Furthermore, we demonstrate that the proposed RCS compensates the non-ideal factors of ReRAM and improves NN accuracy by 5.2% in the XNOR net on CIFAR-10 dataset.