Interconnection lengths and delays estimation for communication links in FPGAs

This paper presents a new stochastic model to predictinterconnection lengths of communication links in FPGAs. Based on a stochastic inter-module routing model, expected length and variance of interconnections have been rigorously derived and, thus, delay can be computed based on the length estimate. The theoretical results are compared with experimental results of lengths and delays, which are obtained from implementations of links circuits in an FPGA. The stochastic model provides an accurate prediction of length with an average error of 6.3%. Results also show that theproposed model produces reliable predictions of delay and therefore the methodology can be applied to early stage planning and design optimization for communication links. Moreover, as a byproduct of this work, we also present in this paper an interesting phenomenon which we term "interconnection fringing". The fringing effect is attributed to the competition for routing resources in a communication link and will lengthen interconnections and, therefore, increase the delay.