ID:188023 The Fitter encountered congestion in the periphery. The likelihood of routing successfully on the next fit attempt is very low.

CAUSE: The Fitter has determined that one or more of the unroutable signals are due to congestion for periphery elements such as I/Os, clock buffers and PLLs. Because many of these nodes are not affected during multiple fit attempts, it is unlikely that subsequent fit attempts will be able to resolve this problem.

ACTION: You can try to move the nodes with the congested signals to different locations to lower the chance of seeing congestion. In addition, if the nodes were not already constrained to an exact location, you can try changing the Fitter's seed, and then re-run the Fitter one or more times. This will result in different placements of the periphery nodes, some of which may be more routable.