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Congestion

Congestion makes the design non-routable that means routing will not be converged if there are congestion in the design. Let's know about congestion in details.

Swasti PujariAssociate Director, Backend Engineering
Published
Updated
Read time
1 min
  • Physical Design
  • Placement
On this page 4 sections
  1. What is Congestion?
  2. Types of Congestion
  3. Reasons for Congestion
  4. Fixes for Congestion

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).

    Written by

    Swasti Pujari

    Associate Director, Backend Engineering at CoreIC Technologies, with 15+ years in VLSI Physical Design and backend engineering. Previously Practice Head at UST Global, leading Physical Design, STA, EMIR, DFT, and Physical Verification. Delivered 3nm, 6nm and 7nm projects for AMD, Intel, and Microchip, and published IEEE research on hybrid AI-EDA floorplanning.

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