An Approach to Gate Assignment and Module Placement for Printed Wiring Boards

High density packaging is one of the most urgent requirements in the design of digital systems. In the assembly of such systems, printed wiring boards (PWB's) are used very often to provide the necessary interconnection among circuit modules. Thus, methods to raise wiring density of PWB's are continually under investigation. Given a router to realize 100 percent wiring, an efficient method for assigning logical gates to circuit modules and for determining the placement of the modules on a given PWB may contribute more toward raising the wirability than improving the existing routing scheme, especially when all available sophisticated routing algorithms have been attempted. The present paper proposes an algorithm to the problem of gate assignment and module placement, to be added to an existing router. It operates on a PDP 11/40 with 24K words core memory and 1.2M words disk storage coupled with a TEKTRONIX 4014 graphics terminal. We also show how effectively the described assignment and placement scheme improves the wirability of the router.