Scrubbing-Aware Placement for Reliable FPGA Systems

Abstract

Field Programmable Gate Arrays (FPGAs) provide complex embedded blocks to ease the development of high-performance computing systems for diverse area applications, including among others space, avionics and health. Although the rich set of features is ever expanding, there is one significant shortcoming of the SRAM-based FPGAs which concerns system designers for applications demanding high reliability: their vulnerability to Single Event Upsets (SEUs) which can cause system malfunction. In this work, we propose a placement approach to improve system reliability by reducing the execution time of configuration memory scrubbing, which can be used in conjunction with other reliability mechanisms proposed in the literature. The proposed placement approach is based on i) an automated floorplanning process to shape and locate the design region(s) and ii) a modified version of the Simulated Annealing placement algorithm aiming to reduce the scrubbing time. First, we performed a set of experiments with three QUIP benchmarks to demonstrate the efficiency of the proposed approach at different device utilization levels. Moreover, we illustrated its effectiveness for three different fault tolerance schemes, where scrubbing plays a different role in each one: i) a TMR microcontroller combined with scrubbing, ii) a soft processor protected by a low-cost mitigation scheme including scrubbing and checkpointing, iii) a JPEG encoder protected by a prioritized scrubbing scheduling scheme based on module criticality levels. The experimental results showed that the proposed approach improves system reliability in all the above schemes by reducing critical timing parameters, such as mean-time-to-detect and mean-time-to-repair. This reduction leads to a modest or high reliability improvement depending on the role of scrubbing in the adopted fault tolerance (FT) scheme.