Magnet Placement and Placement Bound in VLSI Physical Design

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Magnet Placement and Placement Bound in  VLSI Physical Design

These two popular techniques used to optimize placement are Placement Bounds and Magnet Placement. While both techniques aim to improve placement, they differ in their approach, application, and benefits. In this article, we'll look into the details of each technique and compare them to help designers make informed decisions.


1. Placement Bounds

Placement Bounds are a type of constraint that controls the placement of groups of leaf cells and hierarchical cells. They allow designers to group cells to minimize wire length and place the cells at the most appropriate locations. Placement Bounds are particularly useful when timing is critical during placement, and cells need to be placed in close proximity to each other.

Types of placement Bound:

  1. Soft Bound: A Soft Bound is a type of Placement Bound that suggests a preferred placement region for a group of cells. The placement tool tries to place the cells within the specified region, but it is not a hard constraint. If the tool cannot place the cells within the region, it will still try to find an optimal placement.
  2. Hard Bound: A Hard Bound is a type of Placement Bound that strictly enforces the placement of cells within a specified region. The placement tool must place the cells within the region, and it will not consider any other placement options.
  3. Exclusive Bound: An Exclusive Bound is a type of Placement Bound that ensures that cells within the bound do not overlap with cells outside the bound. 

    > create_bound (Synopsys command)
    > create_group, create_boundary_constraint (Innovus command)

2. Magnet Placement

Magnet Placement is a technique used to attract groups of cells /connected cells to specific locations or regions on the chip. This approach enables designers to optimize cell placement to achieve improved congestion, timing, and overall design performance. Magnet Placement is useful in complex floorplan designs, where it can help alleviate congestion and improve overall design performance.


> place_connected (Innovus command)

> magnet_placement (Synopsys Command)



In conclusion, Placement Bounds and Magnet Placement are two distinct techniques used to optimize placement in VLSI design. While both techniques have their strengths and weaknesses, they differ in their approach, application, and benefits. By understanding the differences between these techniques, designers can make informed decisions about which technique to use in their design flow. Ultimately, the choice between Placement Bounds and Magnet Placement depends on the specific design requirements and constraints.


Happy Learning !


#scripting #coding #Tcl #pd #physicaldesign #physicalverification #pv #vlsi #design #india #semiconductor #freshers #professional #hardware #floorplanning #motivation #leadership #magnet #bound #placement #synopsys #cadence












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