A graph-theoretic approach to clock skew optimization

Abstract

This paper addresses the problem of minimizing the clock period of a circuit by optimizing the clock skews. We incorporate uncertainty factors and present a formulation that ensures that the optimization will be safe. In a paper by J.P. Fishburn (see IEEE Trans. on Computers, vol. 39, no. 7, p. 945-951, 1990) the problem of clock period optimization is formulated as a linear program. We first propose an efficient graph-based solution that takes advantage of the structure of the problem. We also show that the results obtained by Fishburn may result in exceedingly large skews, and propose a method to reduce these skews without sacrificing the optimality of the clock period. Experimental results on several ISCAS89 benchmark circuits are provided.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>