Four layer wiring using adjacent-layer vias

An algorithm is presented which, given a two-dimensional wire layout in knock-knee mode, produces a legal wiring (layer-assignment) using only adjacent-layer vias and at most four layers. The previous four-layer wiring algorithm requires technologically impractical vias between non-adjacent layers. This algorithm has important implications for practical automatic wire routing, since many knock-knee layout algorithms rely on the four-layer wiring technique to complete their routing.<
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