Intel® Quartus® Prime Standard Edition User Guide: Design Optimization

ID 683230
Date 11/12/2018
Public
Document Table of Contents
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5.2.2.6. Considerations on Using Auto Sized Regions

If you use Auto Sized Logic Lock (Standard) regions, take into account:
  • Auto/Floating regions cannot be reserved.
  • Verify that your Logic Lock (Standard) region is not empty. If you do not assign any instance to the region, the Fitter reduces the size to 0 by 0, making the region invalid.
  • The region may or may not be associated with a partition. When you combine partitions with Auto Sized Logic Lock (Standard) regions, you get flexibility to solve your particular fitting challenges. However, every constraint that you add reduces the solutions available, and too many constraints can result in the Fitter not finding a solution. Some cases are:
    • If a partition is preserved at synthesis or not preserved, the Logic Lock (Standard) region confines the logic to a specific area, allowing the Fitter to optimize the logic within the partition, and optimize the placement within the Logic Lock (Standard) region.
    • If a partition is preserved at placement, routed, or final; a Logic Lock (Standard) region is not an effective placement boundary, because the location of the partition's logic is fixed.
    • However, if the Logic Lock (Standard) region is reserved, the Fitter avoids placing other logic in the area, which can help you reduce resource congestion.
  • Once the outcome of the Logic Lock (Standard) region meets your specification, you can:
    • Convert the Logic Lock (Standard) region to Fixed Size .
    • Leave the Logic Lock (Standard) region with Auto Sized attribute and use the region as a “keep together” type of function.
    • If the Logic Lock (Standard) region is also a partition, you can preserve the place and route through the partition and remove the Logic Lock (Standard) region entirely.