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.
The following figure shows a non-rectangular static Pblock (shown in yellow)
with an overlapping congestion area (shown in white). In this example, report_design_analysis reports a congestion of level 6 at
the edges of the Pblock. This approach is not
recommended.
The following figure shows the same design but with a rectangular Pblock (shown
in yellow) and a reduced congestion area (shown in white). With this approach, report_design_analysis reports a reduced congestion level
of 5 with no congestion reported at the edge of the rectangular Pblock. This is the
recommended approach.
