Concurrent timing based and routability driven depopulation technique for FPGA packing

In FPGA CAD flow, routability driven algorithms have been introduced to improve feasibility of mapping designs onto the underlying architecture; timing and power driven algorithms have been introduced to meet design specifications. A number of techniques have been proposed to tackle routability, timing or power objectives independently during clustering stage. However, there is minimal work that targets multiple optimization goals. In this paper, we evaluate a clustering technique that targets routability and timing goals simultaneously. We combine the timing-driven T-VPack algorithm with a routability-driven non-uniform depopulation scheme (T-RDPack). Our technique keeps clusters on the critical path fully populated, while depopulating other clusters in the design. This approach has been implemented into the versatile place and route (VPR) toolset. We show that, compared to T-VPack, channel width reductions of 11.5%, 19.1%, 24.7% are achieved while incurring an area overhead of 0.6%, 3.1%, 9.1% respectively with negligible increase in critical path delay, exceeding the performance of T-RPack.