QuickRoute: a fast routing algorithm for pipelined architectures

As interconnect delays begin to dominate logic delays in large circuits, pipelined interconnects will be needed to achieve the highest performance. In FPGAs, this pipelining will be provided by the configurable interconnect architecture itself. This changes the routing problem substantially since the shortest path problem, which is at the core of any router, becomes NP-hard when latency constraints are added. That is, if signals must be routed through a given number of registers between source and destination, an efficient shortest path algorithm like Djikstra's algorithm is no longer an option. We propose here an approximate algorithm that uses simple heuristics to solve the pipelined shortest path problem efficiently. We have incorporated QuickRoute in the PathFinder router to route pipelined interconnects. We present the results achieved with QuickRoute for several circuits with heavily pipelined interconnect which show an improvement over a previously described algorithm.