No Arabic abstract
A mass of data transfer between the processing and storage units has been the leading bottleneck in modern Von-Neuman computing systems, especially when used for Artificial Intelligence (AI) tasks. Computing-in-Memory (CIM) has shown great potential to reduce both latency and power consumption. However, the conventional analog CIM schemes are suffering from reliability issues, which may significantly degenerate the accuracy of the computation. Recently, CIM schemes with digitized input data and weights have been proposed for high reliable computing. However, the properties of the digital memory and input data are not fully utilized. This paper presents a novel low power CIM scheme to further reduce the power consumption by using a Modified Radix-4 (M-RD4) booth algorithm at the input and a Modified Canonical Signed Digit (M-CSD) for the network weights. The simulation results show that M-Rd4 and M-CSD reduce the ratio of $1times1$ by 78.5% on LeNet and 80.2% on AlexNet, and improve the computing efficiency by 41.6% in average. The computing-power rate at the fixed-point 8-bit is 60.68 TOPS/s/W.
`In-memory computing is being widely explored as a novel computing paradigm to mitigate the well known memory bottleneck. This emerging paradigm aims at embedding some aspects of computations inside the memory array, thereby avoiding frequent and expensive movement of data between the compute unit and the storage memory. In-memory computing with respect to Silicon memories has been widely explored on various memory bit-cells. Embedding computation inside the 6 transistor (6T) SRAM array is of special interest since it is the most widely used on-chip memory. In this paper, we present a novel in-memory multiplication followed by accumulation operation capable of performing parallel dot products within 6T SRAM without any changes to the standard bitcell. We, further, study the effect of circuit non-idealities and process variations on the accuracy of the LeNet-5 and VGG neural network architectures against the MNIST and CIFAR-10 datasets, respectively. The proposed in-memory dot-product mechanism achieves 88.8% and 99% accuracy for the CIFAR-10 and MNIST, respectively. Compared to the standard von Neumann system, the proposed system is 6.24x better in energy consumption and 9.42x better in delay.
The inherent dynamics of the neuron membrane potential in Spiking Neural Networks (SNNs) allows processing of sequential learning tasks, avoiding the complexity of recurrent neural networks. The highly-sparse spike-based computations in such spatio-temporal data can be leveraged for energy-efficiency. However, the membrane potential incurs additional memory access bottlenecks in current SNN hardware. To that effect, we propose a 10T-SRAM compute-in-memory (CIM) macro, specifically designed for state-of-the-art SNN inference. It consists of a fused weight (WMEM) and membrane potential (VMEM) memory and inherently exploits sparsity in input spikes leading to 97.4% reduction in energy-delay-product (EDP) at 85% sparsity (typical of SNNs considered in this work) compared to the case of no sparsity. We propose staggered data mapping and reconfigurable peripherals for handling different bit-precision requirements of WMEM and VMEM, while supporting multiple neuron functionalities. The proposed macro was fabricated in 65nm CMOS technology, achieving an energy-efficiency of 0.99TOPS/W at 0.85V supply and 200MHz frequency for signed 11-bit operations. We evaluate the SNN for sentiment classification from the IMDB dataset of movie reviews and achieve within 1% accuracy of an LSTM network with 8.5x lower parameters.
Various hardware accelerators have been developed for energy-efficient and real-time inference of neural networks on edge devices. However, most training is done on high-performance GPUs or servers, and the huge memory and computing costs prevent training neural networks on edge devices. This paper proposes a novel tensor-based training framework, which offers orders-of-magnitude memory reduction in the training process. We propose a novel rank-adaptive tensorized neural network model, and design a hardware-friendly low-precision algorithm to train this model. We present an FPGA accelerator to demonstrate the benefits of this training method on edge devices. Our preliminary FPGA implementation achieves $59times$ speedup and $123times$ energy reduction compared to embedded CPU, and $292times$ memory reduction over a standard full-size training.
A non-volatile SRAM cell is proposed for low power applications using Spin Transfer Torque-Magnetic Tunnel Junction (STT-MTJ) devices. This novel cell offers non-volatile storage, thus allowing selected blocks of SRAM to be switched off during standby operation. To further increase the power savings, a write termination circuit is designed which detects completion of MTJ write and closes the bidirectional current path for the MTJ. A reduction of 25.81% in the number of transistors and a reduction of 2.95% in the power consumption is achieved in comparison to prior work on write termination circuits.
It remains a challenge to run Deep Learning in devices with stringent power budget in the Internet-of-Things. This paper presents a low-power accelerator for processing Deep Neural Networks in the embedded devices. The power reduction is realized by avoiding multiplications of near-zero valued data. The near-zero approximation and a dedicated Near-Zero Approximation Unit (NZAU) are proposed to predict and skip the near-zero multiplications under certain thresholds. Compared with skipping zero-valued computations, our design achieves 1.92X and 1.51X further reduction of the total multiplications in LeNet-5 and Alexnet respectively, with negligible lose of accuracy. In the proposed accelerator, 256 multipliers are grouped into 16 independent Processing Lanes (PL) to support up to 16 neuron activations simultaneously. With the help of data pre-processing and buffering in each PL, multipliers can be clock-gated in most of the time even the data is excessively streaming in. Designed and simulated in UMC 65 nm process, the accelerator operating at 500 MHz is $>$ 4X faster than the mobile GPU Tegra K1 in processing the fully-connected layer FC8 of Alexnet, while consuming 717X less energy.