STA Mastery · All levels

STA Debug Playbook: Tricky Q&A

Senior interview and review questions for STA Debug Playbook.

Section Q&A bank

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

First step when WNS regresses with same netlist?

diagram

[INT][STA][STA-DEBUG-PLAYBOOK]

Q: First step when WNS regresses with same netlist?

A:
Diff SDC, SPEF tag, lib map, and scenario list — constraint or view before PD.

FOLLOW-UP TRAP: Immediate upsize.

What belongs in a STA run manifest?

diagram

[INT][STA][STA-DEBUG-PLAYBOOK]

Q: What belongs in a STA run manifest?

A:
Netlist tag, SDC tag, SPEF tag, lib corners, tool version, scenario set.

FOLLOW-UP TRAP: Untagged nightly runs.

Q&A drill guide

diagram

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

Sketch while answering

diagram

DEBUG ORDER

1. same tags?  2. constraints?  3. view?  4. real path?  5. ECO

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.

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