A Comparative Analysis of Time-Domain and Digital-Domain Hardware Accelerators for Neural Networks

This paper presents a comprehensive analysis of hardware accelerators for neural networks in both the digital and time domains, where the latter includes spatially unrolled (SU) and recursive (REC) architectures. All accelerators are implemented and synthesized in a 65nm CMOS technology. An identical neural network model is implemented in the digital and time domain for comparative purposes in terms of throughput, power consumption, area, and energy efficiency. Post-synthesis results show that SU achieves the highest energy efficiency of 145 TOp/s/W with a throughput of 4 GOp/s. The digital core is the fastest among other cores, whereas REC is the slowest but is the most area-efficient, occupying 0.114 mm
²
. SU is more suited for applications with stringent power constraints and average performance, while REC is better suited for applications where the area is the most important requirement and the throughput is less significant. In contrast, the digital core is preferable for large neural networks and critical applications that require high performance.