Nguyen Kiem Hung; Tran Quoc Long

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The computation complexity and huge memory access bandwidth of the convolutional layers in convolutional neural networks (CNNs) require specialized hardware architectures to accelerate CNN’s computations while keeping hardware costs reasonable for area-constrained embedded applications. This paper presents an RTL (Register Transfer Logic) level microarchitecture of hardware- and bandwidth-efficient high-performance 2D convolution unit for CNN in deep learning. The 2D convolution unit is made up of three main components including a dedicated Loader, a Circle Buffer, and a MAC (Multiplier-Accumulator) unit. The 2D convolution unit has a 2-stage pipeline structure that reduces latency, increases processing throughput, and reduces power consumption. The architecture proposed in the paper eliminates the reloading of both the weights as well as the input image data. The 2D convolution unit is configurable to support 2D convolution operations with different sizes of input image matrix and kernel filter. The architecture can reduce memory access time and power as well as execution time thanks to the efficient reuse of the preloaded input data while simplifying hardware implementation. The 2D convolution unit has been simulated and implemented on Xilinx's FPGA platform to evaluate its superiority. Experimental results show that our design is 1.54× and 13.6× faster in performance than the design in [1] and [2], respectively, at lower hardware cost without using any FPGA’s dedicated hardware blocks. By reusing preloaded data, our design achieves a bandwidth reduction ratio between 66.4% and 90.5%.

Keywords: 2D Convolution, RTL microarchitecture, Circle Buffer, Deep Neural Network, MAC, Loader.