Quartus® Prime Pro Edition User Guide: Design Optimization

ID 683641
Date 4/01/2024
Document Table of Contents Guideline: Increase Router Effort Multiplier

The Router Effort Multiplier controls how quickly the router tries to find a valid solution. The default value is 1.0 and legal values must be greater than 0.

  • Numbers higher than 1 help designs that are difficult to route by increasing the routing effort.
  • Numbers closer to 0 (for example, 0.1) can reduce router runtime, but usually reduce routing quality slightly.
Experimental evidence shows that a multiplier of 3.0 reduces overall wire usage by approximately 2%. Using a Router Effort Multiplier higher than the default value can benefit designs with complex datapaths with more than five levels of logic. However, congestion in a design is primarily due to placement, and increasing the Router Effort Multiplier does not necessarily reduce congestion.
Note: Any Router Effort Multiplier value greater than 4 only increases by 10% for every additional 1. For example, a value of 10 is actually 4.6.