An ASIC Accelerator for QNN With Variable Precision and Tunable Energy Efficiency

This article presents TULIP, a new architecture for a variable precision quantized neural network (QNN) inference. It is designed with the goal of maximizing energy efficiency per classification. TULIP is constructed by arranging a collection of unique processing elements (TULIP-PEs) in a single-instruction-multiple-data (SIMD) fashion. Each TULIP-PE contains binary neurons that are interconnected using multiplexers. Each neuron also has a small dedicated local register connected to it. The binary neurons are implemented as standard cells and used for implementing threshold functions, i.e., an inner-product and thresholding operation on its binary inputs. The neurons can be reconfigured with a single change in the control signals to implement all the standard operations used in a QNN. This article presents novel algorithms for implementing the operations of a QNN on the TULIP-PEs in the form of a schedule of threshold functions. TULIP was implemented as an ASIC in TSMC 40nm-LP technology. A QNN accelerator that employs a conventional multiply and accumulate-based arithmetic processor was also implemented in the same technology to provide a fair comparison. The results show that TULIP is 30\times -50\times more energy-efficient than an equivalent design, without any penalty in performance, area, or accuracy. Furthermore, TULIP achieves these improvements without using traditional techniques such as voltage scaling or approximate computing. Finally, this article also demonstrates how the run-time tradeoff between accuracy and energy efficiency is done on the TULIP architecture.