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

ID 683230
Date 11/12/2018
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3.3.3. Adjusting and Recompiling

Look for obvious problems that you can fix with minimal effort. To identify where the Compiler had trouble meeting timing, perform seed sweeping with about five compiles. Doing so shows consistently failing paths. Consider recoding or redesigning that part of the design.

To reach timing closure, a well written RTL can be more effective than changing your compilation settings. Seed sweeping can also be useful if the timing failure is very small, and the design has already been optimized for performance improvements and is close to final release. Additionally, seed sweeping can be used for evaluating changes to compilation settings. Compilation results vary due to the random nature of fitter algorithms. If a compilation setting change produces lower average performance, undo the change.

Sometimes, settings or constraints can cause more problems than they fix. When significant changes to the RTL or design architecture have been made, compile periodically with default settings and without Logic Lock (Standard) regions, and re-evaluate paths that fail timing.

Partitioning often does not help timing closure, and must be done at the beginning of the design process. Adding partitions can increase logic utilization if it prevents cross-boundary optimizations, making timing closure harder and increasing compile times.