Scenario: Scoreboard Mismatch Chase

Scenario

Nightly regressions show intermittent scoreboard mismatches on a multi-agent SoC test. Failures disappear when one agent is removed, but each agent passes in isolation.

OBSERVED METRIC
Intermittent mismatch rate with poor reproduction until phasing and ordering constraints are locked.

45-MINUTE INTERVIEW FLOW
0-5: scope traffic and SLA context
5-15: map first failing VIP transition
15-25: identify proving artifacts
25-35: propose bounded fix with owner
35-45: state validation matrix and rollback

Common pitfalls

• Blame the DUT before isolating predictor vs monitor alignment.

• Run only single-agent tests for closure evidence.

• Change reference models without versioning or rollback criteria.

Scenario debrief

Score candidate response on traffic framing, timing proof, mitigation boundedness, and regression discipline.

request stream -> controller policy -> VIP timing behavior -> measured outcome

latency/bandwidth trend

Debrief prompts

1. Which VIP timing or queue behavior fails first in evidence?

2. Which smallest safe controller, PHY, or policy change addresses it?

3. Which benchmark + counter gate proves closure under production traffic?

Key takeaways

• Always tie controller and PHY counter shifts to application latency and throughput outcomes.

• Lock firmware timing profile, thermal condition, and DIMM state before comparing VIP captures.

Common pitfalls

• Chasing peak bandwidth while ignoring p99 latency and fairness tails.

• Changing timing guardbands without separating SI noise from scheduling issues.

• Declaring closure without reliability gates, fault injection, and regression replay.