What is Congestion?
If the number of required routing resources exceeds the available routing tracks, the area becomes congested. High congestion leads to detours and poorer results. Severe congestion can make the design non-routable, meaning routing will not converge if congestion persists.
Types of Congestion
There are basically two types of congestion:
- Placement congestion
- Routing congestion.
We need to avoid both the types of congestion in our design.
Reasons for Congestion
- There are different reasons for the congestion which are as follows:
- Bad Floorplan.
- High standard cell density in particular area.
- High pin density in particular area.
- Missing/Small Halos near macro cell.
- Huge number of cells sitting near the macro cell.
Fixes for Congestion
- There are below ways to fix congestion issues in design:
-
- Use blockages in the design, partial blockages help more in optimized way.
- Cell padding
- Module padding
- Decomposition of large cells into small cells (Pin distribution happens).