Timing-driven synthesis spends area where slack is worst. It restructures the critical path, upsizes its gates, and duplicates shared logic to relieve the critical fanout's load.
Technique | What it changes | What it costs |
|---|---|---|
Restructuring | Logic depth of the critical path | Area varies; some paths grow while others shrink. |
Sizing | Drive strength of gates on the worst path | Area grows with each upsize. |
Duplication | Shared logic that isolates the critical fanout | A second copy of the shared cone. |
Groups and weights | Which paths the effort favours | Effort moved away from other paths. |
Lesson | What it covers |
|---|---|
Slack ranks paths so effort lands on the worst one first. | |
Shorter logic depth and a private copy for the critical fanout. | |
Upsizing the worst gates, plus groups and weights that split effort. | |
Worst and total negative slack: what each endpoint total measures. | |
Over-constraining margin, its harm, and rules for stopping. |
One endpoint was fixed while many still fail. The design needs broader effort, not more work on the same path.
This hub runs nothing; its flowchart is a drawing of the lesson structure. The evidence for each claim sits on the five lesson pages, each recorded with Yosys 0.70 and ABC and listed in that page's frame.