FPGA Routing Pathfinder [Ebeling, et al., 1995] Introduced negotiated congestion During each routing iteration, route nets using shortest path Allows overuse (congestion) of routing resources If congestion exists (illegal routing) Update cost of congested resources based on the amount of overuse Rip-up all routes and reroute all nets 2 congestion 2

2 FPGA Routing VPR – Versatile Place and Route [Betz, et al., 1997] Uses modified Pathfinder algorithm Increase performance over original Pathfinder algorithm Routability-driven routing Goal: Use fewest tracks possible Timing-driven routing Goal: Optimize circuit speed Routing Resource Graph Resource Graph Route Rip-up Done! congestion? illegal? no yes

3 JIT FPGA Routing Riverside On-Chip Router (ROCR) Represent routing nets between CLBs as routing between SMs Resource Graph Nodes correspond to SMs Edges correspond to channels between SMs Capacity of edge equal to the number of wires within the channel Requires much less memory than VPR as resource graph is much smaller SM 0/4