For Pblocks with CONTAIN_ROUTING enabled, the router has less solution space at the corners of the Pblock. To avoid unroutable situations, Xilinx recommends making Pblocks as rectangular as possible. Using another shape results in more corners for the Pblock, which can introduce congestion at those corners.
In the following example, report_design_analysis reports a congestion of
level 6 at the edges of a non-rectangular static Pblock. This approach is
not recommended.
Figure 1. Non-Rectangular Static Pblock with Congestion at the
Corners
The following example shows the same design but with a rectangular Pblock. With this
approach, report_design_analysis reports a reduced congestion level 5
with no congestion reported at the edge of the Pblock. This is the recommended
approach.
Figure 2. Rectangular Static Pblock with Reduced Congestion
