oCongestion Maps: Use the PnR tool’s GUI to visualize the congestion map generated after trial/global routing. Identify hotspots (high overflow areas, usually color-coded red/orange). Check both horizontal and vertical layer congestion.
- reportCongestion - list the most congested regions.
Reasons could be - High Cell Density - Macro Pin Areas - Narrow Channels - Bad Floorplan - Specific Logic: Are certain types of logic (e.g., large muxes, data path logic) concentrating connections in one area?
- Fixing/Preventing Congestion:
- Update Floorplan
Placement Blockages (Partial):
Maximum Utilization/Density Constraints
Cell Spreading/Padding:
- Cell Padding:
- Optimize Placement Settings:
Congestion-Driven Effort: setPlaceMode –congEffort high). The tool will prioritize reducing congestion, potentially at the expense of timing/wirelength initially.
Guidance (Bounds/Regions): Use placement bounds (guides, regions)
Congestion Analysis/Fixing: https://vlsiweb.com/congestion-analysis/