Scenario: Retiming Debate: Interview Drills

Interview drills

Interview Drills for Scenario: Retiming Debate focuses on frequency target miss versus latency and verification budget. The goal is to connect observed QoR movement to mechanism, ownership, and regression risk.

PROMPT
You observe frequency target miss versus latency and verification budget in Scenario: Retiming Debate. Walk through root cause and closure plan.

STRONG ANSWER
1. Names run context and affected QoR lane.
2. Explains Retiming debate evaluates whether register movement is safer than RTL pipeline edits under schedule and formal constraints.
3. Requests retiming option sheet, equivalence plan, risk matrix.
4. Proposes one reversible fix and full regression scope.

WEAK ANSWER
Jumps to random tool switches without mechanism evidence.

Whiteboard diagram

Retiming debate matrix

retime now?
benefit: Fmax
cost: formal + latency + schedule
decision by risk budget

Root-cause narration

ROOT-CAUSE TREE — Scenario: Retiming Debate

frequency target miss versus latency and verification budget 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

Retiming debate evaluates whether register movement is safer than RTL pipeline edits under schedule and formal constraints.

Metric: frequency target miss versus latency and verification budget