BU-Router: Researching on Techniques of Global Router

Abstract

Variety of routing approaches are employed by global routers in the VLSI circuit designs. Rip-up and reroute, as a conveniently implemented method, is widely used in most of modern global routers. Maze algorithm is always performed iteratively as the final technique to eliminate overflow. Maze algorithm and its ramifications can obtain an optimum solution. However, it will cost much CPU time if being used impertinently. In this work, we present a global router called Bottom-Up Router (BU-Router), with an optimized maze algorithm, which is based on multi-source multi-sink maze. BU-Router processes not the nets but the segments of nets in a sequence ordered by the length. In the progress, segments will be fixed on the global route graph edge, when the edge is saturated, which is as the basis, also known as bottom. Then the edge will be set as a blockage, which wont accept path goes through it any more. This means the edge will push the possible congestion in the future. Besides this, BU-Router optimized cost function in two ways: make the function adaptive and congestion center avoidable. Additionally, a specific optimized maze algorithm is proposed for routing a long distance segment so as to reduce the run-time.