When analyzing the Placer Final Congestion Reporting Table of your design for Congestion and Timing QoR, look for the following:
- If a high level of LUT usage exists, examine the instances that have a high percentage of LUT6s in the Complexity report.
- In case of high RAMB or DSP utilization in the congested area, check for Pblock constraints that might be limiting the available placement area of the reported modules. Use various targeted placement directives to relieve congestion such as the BlockPlacement or SpreadLogic directives. In some cases, it might be beneficial to reuse the RAMB or DSP placement from a previous run that showed low congestion and resulted in good Timing QoR.
The following figure shows an example of the Placer Final Congestion Reporting table. Using this report, you can examine areas of the device defined by the Congestion window along with the modules residing in that window. The resource usage percentages gives an indication of the types of resources located in the congested area.
Figure 1. Example Placer Final Congestion Reporting Table