STA Mastery · All levels

MMMC Signoff: Tricky Q&A

Senior interview and review questions for MMMC Signoff.

Section Q&A bank

Use these drills after completing all topics in MMMC Signoff. Answer with corner/mode/view, path group, metric, artifact, ECO, and regression.

What is an MMMC scenario?

diagram

[INT][STA][MMMC-SIGNOFF]

Q: What is an MMMC scenario?

A:
A corner + mode + lib + RC view combination run as one STA session.

FOLLOW-UP TRAP: Signoff on typical corner only.

Why map libraries per corner?

diagram

[INT][STA][MMMC-SIGNOFF]

Q: Why map libraries per corner?

A:
Cell delays are PVT-dependent; wrong lib makes slack meaningless.

FOLLOW-UP TRAP: Using TT lib at SS corner.

Implementation vs signoff view delta?

diagram

[INT][STA][MMMC-SIGNOFF]

Q: Implementation vs signoff view delta?

A:
Expected due to RC corners; track delta bounds, not single-view WNS.

FOLLOW-UP TRAP: Panic on every view difference.

Q&A drill guide

diagram

CONSTRAINT -> VIEW -> PATH -> METRIC -> ECO -> REGRESSION

Sketch while answering

diagram

MMMC

corners (ss/tt/ff) x modes (func/test) x views (signoff RC)
= scenario set -> min(WNS) is signoff

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.

Practice this lesson