Venkateswaran and Mazumder : Design for Surface - Mounted Pcb Routing

Absfract-The printed circuit boards (PCB’s) for the 1990’s can be characterized by higher circuit densities, multiple routing layers, newer packaging technologies, and demand for lower manufacturing costs. The task of connecting all the traces on such a complex board will become more and more time consuming. This paper presents the issues involved in the design of a special-purpose processing array system, called HAM, which will accelerate such compute-intensive wire routing tasks. It is especially suited for double-sided surface-mounted boards which require complex three-dimensional search operations over multiple wiring planes. The novel features of the design include a hexagonal interconnection scheme to improve workload distributions during multilayer concurrent search operations and the VLSI custom design of the processors. Particular emphasis has been placed on the demands of maze routing such as in the allocation of the routing database on the multiple processors, design of buffer stores for maintaining the frontier-lists, etc. A novel scheme of cell-address propagation, which is quite different from the traditional grid-coordinate approach is discussed. This provides for rapid lookup of pertinent routing information and can be extended to any distributed memory multiprocessor system. A global pipelining scheme of cell updates and expands is discussed. Experimental results are presented relating the speedup to Merent criteria such as number of processors and size of the local memory for two different modes of parallel wave propagation.