Modelling and compensating for clock skew variability in FPGAs

As integrated circuits are scaled down it becomes difficult to maintain uniformity in process parameters across each individual die. To avoid significant performance loss through pessimistic over-design new design strategies are required that are cognisant of within-die performance variability. This paper examines the effect of process variability on the clock resources in FPGA devices. A model of variation in clock skew in FPGA clock networks is presented. Techniques for reducing the impact of variations on the performance of implemented designs are proposed and analysed, demonstrating that skew variation can be reduced by 70% or more through a combination of phase adjustment and clock rerouting. Measurements on a Virtex-5 FPGA validate the feasibility and benefits of the proposed compensation strategies.