On the Placement and Granularity of FPGA Configurations

Dynamic FPGA reconfiguration represents an overhead that can be critical to the performance of a realised circuit. To address this problem, This work presents a technique that is applicable at the times of loading the configuration data on the device. The technique involves reusing the on-chip configuration fragments to implement the next configuration thereby reducing the amount of data that must be externally transferred to the configuration memory. This work provides an analysis of the effect of circuit placement and configuration granularity on configuration reuse. The problem of finding placements of each circuit in a sequence of circuits so as to maximize configuration re-use is considered in detail. A greedy solution to this NP complete problem was found to reduce configuration overheads by less than 5% for a benchmark set. The effect of configuration granularity on configuration reuse was also considered and it was found that reducing the size of the unit of configuration allowed us to reduce the size of the benchmark configurations by 41%