Clock distribution architectures: a comparative study

Abstract

This paper evaluates and compares different clock architectures such as mesh, tree and their hybrids, on several industrial designs. The goal of our study is to gain a quantitative understanding of engineering trade-offs between different architectures with respect to clock skew, latency, timing uncertainty, and power. This understanding will lead to guidelines for determining the best clock architecture for the design specification and constraints. To the best of our knowledge, no work has been published on evaluating and comparing these architectures on real industrial designs. Our study shows that mesh-based architectures are better than tree architectures for skew (< 1ps skew) and are more robust to variations (18% reduction in timing uncertainty as compared to tree). The power penalty associated with a mesh as compared to a tree was found to be between 10-40%. Use of multiple meshes can help reduce the power penalty