An Energy Efficient Time-Multiplexing Computing-in-Memory Architecture for Edge Intelligence

Abstract

The growing data volume and complexity of deep neural networks (DNNs) require new architectures to surpass the limitation of the von-Neumann bottleneck, with computing-in-memory (CIM) as a promising direction for implementing energy-efficient neural networks. However, CIM’s peripheral sensing circuits are usually power- and area-hungry components. We propose a time-multiplexing CIM architecture (TM-CIM) based on memristive analog computing to share the peripheral circuits and process one column at a time. The memristor array is arranged in a column-wise manner that avoids wasting power/energy on unselected columns. In addition, digital-to-analog converter (DAC) power and energy efficiency, which turns out to be an even greater overhead than analog-to-digital converter (ADC), can be fine-tuned in TM-CIM for significant improvement. For a 256*256 crossbar array with a typical setting, TM-CIM saves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$18.4\times $ </tex-math></inline-formula> in energy with 0.136 pJ/MAC efficiency, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$19.9\times $ </tex-math></inline-formula> area for 1T1R case and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$15.9\times $ </tex-math></inline-formula> for 2T2R case. Performance estimation on VGG-16 indicates that TM-CIM can save over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$16\times $ </tex-math></inline-formula> area. A tradeoff between the chip area, peak power, and latency is also presented, with a proposed scheme to further reduce the latency on VGG-16, without significantly increasing chip area and peak power.