Fast interconnect optimization

As the continuous trend of Very Large Scale Integration (VLSI) circuits technology scaling and frequency increases, delay optimization techniques for interconnect are increasingly important for achieving timing closure of high performance designs. For the gigahertz microprocessor and multi-million gate ASIC designs it is crucial to have fast algorithms in the design automation tools for many classical problems in the field to shorten time to market of the VLSI chip. This research presents algorithmic techniques and constructive models for two such problems: (1) Fast buffer insertion for delay optimization, (2) Wire sizing for delay optimization and variation minimization on non-tree networks. For the buffer insertion problem, this dissertation proposes several innovative speedup techniques for different problem formulations and the realistic requirement. For the basic buffer insertion problem, an O(n log2 n) optimal algorithm that runs much faster than the previous classical van Ginneken??s O(n2) algorithm is proposed, where n is the number of buffer positions. For modern design libraries that contain hundreds of buffers, this research also proposes an optimal algorithm in O(bn2) time for b buffer types, a significant improvement over the previous O(b2n2) algorithm by Lillis, Cheng and Lin. For nets with small numbers of sinks and large numbers of buffer positions, a simple O(mn) optimal algorithm is proposed, where m is the number of sinks. For the buffer insertion with minimum cost problem, the problem is first proved to be NP-complete. Then several optimal and approximation techniques are proposed to further speed up the buffer insertion algorithm with resource control for big industrial designs. For the wire sizing problem, we propose a systematic method to size the wires of general non-tree RC networks. The new method can be used for delay optimization and variation reduction.