Towards integration of quadratic placement and pin assignment

Abstract

Pins serve as both the logical and physical interface between two levels in a hierarchical flow. Pin assignment is the placement of pins on the boundary of a chip or macro. Proper pin placement has a large influence on wire length. Experiments indicate a spread in wire length up to over 20%. To address the pin assignment problem, a modification to the well-known and widely used quadratic placement is introduced. This modification allows for the integration between pin assignment and global placement. Wire length within macros is minimized, while top-level considerations such as the relative position of macro and clusters of cells are taken into account in the form of a side assignment. As indicated by experimental results, integration is promising. More research is necessary to fully exploit the ideas in this paper, and assess the practical impact of the approach.