Bitstream relocation with local clock domains for partially reconfigurable FPGAs

Abstract

Partial Reconfiguration (PR) of FPGAs presents many opportunities for application design flexibility, enabling tasks to dynamically swap in and out of the FPGA without entire system interruption. However, mapping a task to any available PR region (PRR) requires a unique partial bitstream for each PRR. This replication can introduce significant overheads in terms of bitstream storage and communication requirements. Previous research in partial bitstream relocation can alleviate these overheads by transforming a single partial bitstream to map to any available PRR. However, careful steps are necessary to ensure proper functionality of relocated partial bitstreams and may result in clock routing inefficiencies. These routing inefficiencies can be alleviated by using regional clock resources introduced in the Virtex-4 FPGAs to implement local clock domains. PRRs can internally drive local clock domains, enabling each PRR to vary its clock frequency with respect to a single global clock signal, as opposed to sending multiple global clock signals (one for each desired clock frequency) to each PRR. We introduce this novel local clock domain (LCD) concept, which provides enhanced PR design flexibility. However, integration of LCDs and partial bitstream relocation introduces new challenges. In this paper, we identify motivating application domains for this integration, analyze integration benefits, and provide a detailed integration methodology.