Two-dimensional systolic-array architecture for pixel-level vision tasks

This paper presents ongoing work on the design of a two-dimensional (2D) systolic array for image processing. This component is designed to operate on a multi-processor system-on-chip. In contrast with other 2D systolic-array architectures and many other hardware accelerators, we investigate the applicability of executing multiple tasks in a time-interleaved fashion on the Systolic Array (SA). This leads to a lower external memory bandwidth and better load balancing of the tasks on the different processing tiles. To enable the interleaving of tasks, we add a shadow-state register for fast task switching. To reduce the number of accesses to the external memory, we propose to share the communication assist between consecutive tasks. A preliminary, non-functional version of the SA has been synthesized for an XV4S25 FPGA device and yields a maximum clock frequency of 150 MHz requiring 1,447 slices and 5 memory blocks. Mapping tasks from video content-analysis applications from literature on the SA yields reductions in the execution time of 1-2 orders of magnitude compared to the software implementation. We conclude that the choice for an SA architecture is useful, but a scaled version of the SA featuring less logic with fewer processing and pipeline stages yielding a lower clock frequency, would be sufficient for a video analysis system-on-chip.