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ECO Regression Matrix: Step-by-Step Walkthrough

Step-by-Step Walkthrough for ECO Regression Matrix.

Step-by-step analysis walkthrough

Use when you own ECO Regression Matrix in a timing war room.

  1. Open signoff scenario list — note worst WNS corner.

  2. report_timing -max/-min on failing group.

  3. Trace launch and capture clocks on critical path.

  4. Check exceptions and generated clocks on path.

  5. Break down cell vs net delay.

  6. Compare implementation vs signoff view if delta suspicious.

  7. Assign owner: RTL, synth, PD, CTS, SI.

  8. Propose ECO with hold/SI check plan.

  9. Run regression matrix.

  10. Update closure dashboard and memo.

Artifacts to collect

  • regression manifest, corner comparison table, signoff approval

  • SDC file

  • SPEF tag

  • MMMC scenario list

  • ECO ticket

Decision memo template

diagram
STA DECISION MEMO — ECO Regression Matrix
corner/mode:
WNS/TNS:
hypothesis:
ECO:
regression:
owners: STA lead, CAD owner, program lead

Reference visuals

Post-ECO regression

diagram
ECO REGRESSION CHECKLIST
[ ] all MMMC scenarios
[ ] SI re-run
[ ] power/leakage delta
[ ] equivalence / LVS if logical ECO
[ ] signoff memo updated

STA deep dive

ECO without regression is a coin flip.

Concept diagram

diagram
ECO LOOP

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

Metric graph

diagram
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?

Key takeaways

  • State corner, mode, view, and database tag with every slack claim.

  • Run setup and hold plus MMMC regression after every ECO.

Common pitfalls

  • Comparing STA runs with different SPEF or SDC tags.

  • Broad false_path to green-wash violations.

  • Setup-only ECO without hold check.

Principal STA review addendum

Every ECO must re-run the agreed MMMC matrix plus SI; regression hygiene prevents shipping a fix that breaks another corner.

Metric: corners re-run, new violations introduced, signoff delta

Practice this lesson