The techniques described have been implemented in a multilayer channel router called Chameleon. Chameleon consists of two stages: a partitioner and a detailed router. The partitioner divides the problems into two-layer and three-layer subproblems such that global channel area is minimized. The detailed router then implements the connections using generalizations of the algorithms used in YACR2 (see ibid., vol.CAD-4, no.3, p.208-19, 1985). In particular, a three-dimensional maze router is used for the vertical connections; this methodology is effective even when cycle constraints are present. Chameleon has produced optimal results on a wide range of industrial and academic examples for a variety of layer and pitch combinations, and can handle a variety of technology constraints.>

A modification of the classical Simulated Annealing algorithm for the macro-cell placement problem is proposed for implementation on multiprocessor systems. The algorithm has been implemented on the Sequent Balance 8000, a multiprocessor system with a shared-memory architecture. Experimental results show that the new algorithm obtains results comparable in quality to those of the single processor version; processor utilization is greater than 80 percent using up to eight processors.

New techniques for routing general multi-layer channels are introduced. These techniques can handle a variety of technology constraints. For example, linewidth and line-to-line spacing can be specified independently for each layer, and contact stacking can be allowed or forbidden. These techniques have been implemented in a new multi-layer channel router called Chameleon. Chameleon consists of two stages: a partitioner and a detailed router. The partitioner divides the problem into two and three-layer subproblems such that global channel area is minimized. The detailed router then implements the connections using generalizations of the algorithms used in YACR2. In particular a three-dimensional maze router is used which guarantees that any problem can be routed even when cyclic constraints are present. Chameleon produces optimal results on a wide range of industrial and academic examples for any number of layers and pitch combinations.