ECO Timing Closure

Section goal

Setup/hold closure order, physical vs logical ECO, useful skew, sizing, VT swap, and regression discipline.

How to study this section

1. Start with the topic hub to learn the contract.

2. Use mechanism and reports pages to connect rules to metrics.

3. Use debug and worked-example pages for interview and on-call practice.

4. Close with checklist and PPA impact before signing any change.

Topics

1. setup-hold-closure-order/ — Setup / Hold Closure Order

2. eco-physical-vs-logical/ — ECO Physical vs Logical

3. useful-skew-tradeoffs/ — Useful Skew Tradeoffs

4. eco-regression-matrix/ — ECO Regression Matrix

Related topics

• STA course hub

STA deep dive

ECO without regression is a coin flip.

Concept diagram

ECO LOOP

failing path -> fix -> setup check -> hold check -> SI -> MMMC matrix

Metric graph

ECO PROGRESS

WNS
 0 |              o target
-50|        o
-100|   o baseline
    +-----------------> ECO #

Reports and artifacts

• pre/post WNS

• hold delta

• leakage delta

• ECO ticket log

Mini case study

48-hour tapeout crunch: VT swap fixed setup; hold fixed with route on short path — order mattered.

Debug branches

• Never ship setup-only proof

• Logical ECO needs equivalence

Senior review question

Ask: what corner/mode/view proves this topic is closed or failing?