Refine Placement & Detailed Placement

Refine Placement (Legalization)

  • Legalization makes the rough solution from global placement legal (i.e., no placement constraint violation) by moving modules around locally.
  • Looking at the Congestion, Timing and Power the objects are moved within the region to achieve the goal.
  • Refine placement takes care of overlaps of cells/modules within the core area and correct it by moving the cell/module nearer.

There are number of tool options which we can use for refining the placement, like you can set some micron distance so that tool will not move those cells more than specified distance.

Detailed Placement

  • Detailed placement further improves the legalized placement solution in an iterative manner by rearranging a small group of modules in a local region while keeping all other modules fixed.
  • Detailed placement is the final stage of placement. All the final quality improvements will occur at this stage. The following things need to be taken care of during detailed placement:
    • Congestion
    • Timing
    • Power

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