Is wire tapering worthwhile?

Wire sizing and buffer insertion/sizing are critical optimizations in deep submicron design. The past years have seen several studies of buffer insertion, wire sizing, and their simultaneous optimization. When wiring long interconnect, tapering, i.e., reducing the wire width as the distance from the driver increases, has proven effective. However tapering is not widely utilized in industry since it is difficult to integrate into a complete routing methodology. The article examines the benefits of wire sizing with tapering when combined with buffer insertion. We perform several experiments with actual IBM technologies. Results indicate that wire tapering reduces delay typically by less than 5% compared to uniform wire sizing, when buffers can be inserted. Consequently, we suggest that it may not be worthwhile to maintain a routing methodology that supports wire tapering.