Scenario: QoR Storm: Interview Drills

Interview drills

Interview Drills for Scenario: QoR Storm focuses on overnight WNS/TNS regression with no RTL intent change. The goal is to connect observed QoR movement to mechanism, ownership, and regression risk.

PROMPT
You observe overnight WNS/TNS regression with no RTL intent change in Scenario: QoR Storm. Walk through root cause and closure plan.

STRONG ANSWER
1. Names run context and affected QoR lane.
2. Explains QoR storms test run-hygiene fundamentals: constraint diffs, library updates, and compile switches before speculative ECO.
3. Requests scenario brief, run manifest diff, triage timeline.
4. Proposes one reversible fix and full regression scope.

WEAK ANSWER
Jumps to random tool switches without mechanism evidence.

Whiteboard diagram

QoR storm triage board

overnight regression
  -> manifest diff
  -> isolate first drift
  -> reversible fix

Root-cause narration

ROOT-CAUSE TREE — Scenario: QoR Storm

overnight WNS/TNS regression with no RTL intent change regressed
        |
   same RTL/constraints tag?
     /              \
   no                yes
   |                  |
input drift      transform side-effect
 /    \             /         \
SDC    libs      mapping      physical estimate
diff   diff      choice       mismatch

Synthesis deep dive

Interview readiness comes from repeatable QoR reasoning under pressure.

Concept diagram

INTERVIEW ANSWER SHAPE

context -> metric -> mechanism -> fix -> regression -> ownership

Metric graph

PANEL SCORING

clarity      ███████
mechanism    ██████
regression   █████

Reports and artifacts

• mock scorecard

• scenario debrief

• Q&A coverage

• framework adherence

Mini case study

Candidate improved by replacing tool-command answers with evidence-driven closure narratives.

Debug branches

• State assumptions first

• Defend option tradeoffs

• Close with rollback/regression

Senior review question

Ask: what evidence proves this QoR move is real and stable?

Key takeaways

• State exact run context (RTL, SDC, libs, switches) with every QoR claim.

• Re-run timing, area, and power regressions after each synthesis ECO.

Common pitfalls

• Comparing runs with mismatched constraints or library views.

• Timing-only fixes that violate power or area budgets.

• Skipping equivalence checks after structural changes.

Principal synthesis review addendum

QoR storms test run-hygiene fundamentals: constraint diffs, library updates, and compile switches before speculative ECO.

Metric: overnight WNS/TNS regression with no RTL intent change