A Row-Based Algorithm for Non-Integer Multiple-Cell-Height Placement

Abstract

A circuit design with non-integer multiple cell height (NIMCH) is more flexible for optimizing area, timing, and power simultaneously. A cell with a larger height provides higher pin accessibility, higher drive strength, and shorter delay. In contrast, one with a smaller height has a smaller area, pin capacitance, and power consumption. Such NIMCH design must satisfy additional layout constraints that existing tool flows cannot handle well. This paper presents a row-based algorithm for non-integer multiple-cell-height placement. Our algorithm consists of two main techniques: (1) a k-mean-based clustering method to assign heights to each row to define the regions of particular cell heights, and (2) a legalization method to move cells to satisfy NIMCH constraints. Experimental results show that our approach can significantly reduce the average routed wirelength and the average total power compared with the state-of-the-art approach.