Derate on the Capture Clock Path Only

• With set_timing_derate -early, only the capture clock is taken at its minimum for the setup check.
• All the variation is therefore applied to the capture side.

KEY For setup, only the capture clock is taken at min, so derate is applied on the capture clock path.

Fixing Hold After Tapeout

• Only if the violation is due to a missing timing arc.
• In every other case there is no way to fix hold after tapeout.

KEY Post-tapeout hold can only be fixed if it stems from a missing timing arc; otherwise it cannot.

Same Path Being the Critical One

• At the same PVT, no.
• At different PVT conditions, yes.
• Cell delay does not scale uniformly with voltage.
• Delay at 0.5 V can be roughly 10x the delay at 2.0 V.
• To handle this, choose cells whose delay scaling is small across all those conditions.

KEY Same path can be critical only across different PVTs, because delay scales non-uniformly with voltage.

Debug Steps for Hold Fixing

• Review the list of cells provided for hold fixing.
• Confirm those cells are actually usable - they should not have the dont_use attribute set to 1.
• Verify the command that makes these cells available for hold (for example set_prefer with the min option).
• Check that the hold corner is available.
• Check that the hold MCMM scenario is available.

KEY For hold-fix debug: check the cell list, dont_use flags, enabling commands, and the hold corner/scenario.