Coprocessor design for multilayer surface-mounted PCB routing

The authors present the issues involved in the design of a special-purpose processing array system, called HAM, which accelerates computationally 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. A cell-address propagation scheme, which is quite different from the traditional grid-coordinate approach, is discussed. It provides 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 various criteria for two different modes of parallel wave propagation