Timing-aware power-optimal ordering of signals

Abstract

A computationally efficient technique for reducing interconnect active power in VLSI systems is presented. Power reduction is accomplished by simultaneous wire spacing and net ordering, such that cross-capacitances between wires are optimally shared. The existence of a unique power-optimal wire order within a bundle is proven, and a method to construct this order is derived. The optimal order of wires depends only on the activity factors of the underlying signals; hence, it can be performed prior to spacing optimization. By using this order of wires, optimality of the combined solution is guaranteed (as compared with any other ordering and spacing of the wires). Timing-aware power optimization is enabled by simultaneously considering timing criticality weights and activity factors for the signals. The proposed algorithm has been applied to various interconnect layouts, including wire bundles from high-end microprocessor circuits in 65 nm technology. Interconnect power reduction of 17% on average has been observed in such bundles.