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SerDes & High-Speed I/O: Tricky Q&A

Senior interview and review questions for SerDes & High-Speed I/O.

Section Q&A bank

Use these drills after completing all topics in SerDes & High-Speed I/O. Answer with boundary, mode, metric, artifact, owner, and regression.

Link comes up but BER spikes later. First hypothesis?

diagram

[INT][AMS][SERDES-HIGH-SPEED-IO]

Q: Link comes up but BER spikes later. First hypothesis?

A:
Margin collapse from SI/thermal drift or unstable adaptation despite initial training success.

FOLLOW-UP TRAP: Declaring protocol clean after first link-up.

What evidence separates firmware timeout bug from SI issue?

diagram

[INT][AMS][SERDES-HIGH-SPEED-IO]

Q: What evidence separates firmware timeout bug from SI issue?

A:
Correlating state transitions with lane margin and analog error indicators under controlled conditions.

FOLLOW-UP TRAP: Changing timeout first and re-testing once.

Q&A drill guide

diagram

BOUNDARY -> MECHANISM -> METRIC -> ARTIFACT -> FIX -> REGRESSION

Sketch while answering

diagram

SERDES FLOW

training -> equalization -> lane margin -> protocol stability

Key takeaways

State boundary, mode, and evidence tag with every claim.
Always align analog, digital, and physical owners before signoff decisions.

Common pitfalls

Fixing averages while tails still fail.
Skipping package/supply evidence in jitter or SerDes issues.
Shipping with waivers that lack owner and expiration criteria.

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