The low communication bandwidth between memory and processing units in conventional von Neumann machines does not support the requirements of emerging applications that rely extensively on large sets of data. More recent computing paradigms, such as high parallelization and near‐memory computing, help alleviate the data communication bottleneck to some extent, but paradigm‐shifting concepts are required. In‐memory computing has emerged as a prime candidate to eliminate this bottleneck by colocating memory and processing. In this context, resistive switching (RS) memory devices is a key promising choice, due to their unique intrinsic device‐level properties, enabling both storing and computing with a small, massively‐parallel footprint at low power. Theoretically, this directly translates to a major boost in energy efficiency and computational throughput, but various practical challenges remain. A qualitative and quantitative analysis of several key existing challenges in implementing high‐capacity, high‐volume RS memories for accelerating the most computationally demanding computation in machine learning (ML) inference, that of vector‐matrix multiplication (VMM), is presented. The monolithic integration of RS memories with complementary metal–oxide–semiconductor (CMOS) integrated circuits is presented as the core underlying technology. The key existing design choices in terms of device‐level physical implementation, circuit‐level design, and system‐level considerations is reviewed and an outlook for future directions is provided.
Memristor as an emerging history dependent nanometer scaled element will play an important role in future nanoelectronic computing technologies. Some pure and hybrid memristor-based implementation techniques have been proposed in recent years. Material implication logic is one of the significant areas for memristor-based logic implementation. In this paper a memristor-based linear feedback shift register is implemented based on material implication logic. It is implemented by 8 memristors which is considerably used less area in comparison with conventional CMOS-based peers. Also the proposed memristor-based LFSR circuit needs 55 computational steps for generating a 4-bits number.
14 February 2018 in IEEE Transactions on Very Large Scale Integration (VLSI) Systems
Memristor crossbar architectures are considered as one of the most promising platforms for future memory, logic, and in-memory computing applications. This paper presents a 2M1M crossbar architecture, capable of memory and logic applications, based on a transistor-less memory cell, which behaves as a switching circuit. The proposed memory cell consists of two access and one target memristors that utilize a gating structure by access devices to reduce sneak path effect. This paper has considerably lower wiring density and lower number of memristors per bit compared with its peers. Therefore, it can be a suitable structure for high-density memory and logic applications. In addition to its in-memory computing capabilities, 2M1M structure as a memory offers higher density and less energy consumption in comparison with conventional CMOS-based static random access memory. In comparison with previous works, simulation results show significant improvements in basic implementation costs of the memory cell in terms of write time (1.11 ns), read time (200 ps), density (80 Gb/cm²), energy consumption (23.2x 10⁻³ fJ/bit), and wiring complexity. Also, it has a sneak path current of 90-nA per memory cell operation which is considerably lower compared with its peers.
Neuromorphic Computing In article number 1900189, Mostafa Rahimi Azghadi, Yao-Feng Chang, and co-workers discuss challenges and opportunities and shed light on recent advances in CMOS, SiOx-based mem...
21 March 2023 in Memories - Materials, Devices, Circuits and Systems
Spiking neural networks (SNNs) are well-suited for neuromorphic hardware due to their biological plausibility and energy efficiency. These networks utilize sparse, asynchronous spikes for communication and can be binarized. However, the training of such networks presents several challenges due to their non-differentiable activation function and binarized inter-layer data movement.The well-established backpropagation through time (BPTT) algorithm used to train SNNs encounters notable difficulties because of its substantial memory consumption and extensive computational demands. These limitations restrict its practical utility in real-world scenarios. Therefore, effective techniques are required to train such networks efficiently while preserving accuracy. In this paper, we propose Binarized Spike Timing Dependent Gradient (BSTDG), a novel method that utilizes presynaptic and postsynaptic timings to bypass the non-differentiable gradient and the need of BPTT. Additionally, we employ binarized weights with a threshold training strategy to enhance energy savings and performance. Moreover, we exploit latency/temporal-based coding and the Integrate-and-Fire (IF) model to achieve significant computational advantages. We evaluate the proposed method on Caltech101 Face/Motorcycle, MNIST, Fashion-MNIST, and Spiking Heidelberg Digits. The results demonstrate that the accuracy attained surpasses that of existing BSNNs and single-spike networks under the same structure. Furthermore, the proposed model achieves up to 30× speedup in inference and effectively reduces the number of spikes emitted in the hidden layer by 50% compared to previous works.