A performance-driven I/O pin routing algorithm

Abstract

This paper presents a performance-driven I/O pin routing algorithm with special consideration of wire uniformity. First, a topological routing based on a min-cost max-flow algorithm is proposed. In this phase, an exponential weight function is used to guide the flow distribution which is very helpful in distributing wires, globally and uniformly, on the whole routing area. Then a physical routing phase is applied to implement one-to-one connection between chip pads and I/O pins, which focuses on the wire uniformity of the fanout area nearby the periphery of chip pads. Finally, a balanced position based wire polishing approach is proposed to further improve the local wire uniformity which tries to modify each wire into a smooth curve instead of broken line while satisfying the specified design rules such as wire-wire pitch and wire-pin pitch. A routing cost function is adequately defined to guide the whole routing process which leads to a good trade-off between wire uniformity and wire length. The algorithm has been implemented and tested on up to 10-ring 600-pin PGA and the experimental results are very promising.