What makes a design difficult to route.

ABSTRACTTraditionally, the goal of physical synthesis has been to produce a physical realization of the input netlist that meets its timing constraints with minimum area. However, design routability has emerged from a secondary objective to perhaps the primary objective, in no small part due to the myriad of rules and constraints that emerge with each successive technology. This work overviews the complexities with modeling congestion during physical synthesis and discusses how optimizations may be able to provide some relief.