Synthesis & Logic Optimization · All levels
Scenario: Retiming Debate: Comparison Matrix
Comparison Matrix for Scenario: Retiming Debate.
Comparison matrix
Strong answers compare options by risk, evidence, and regression burden.
+------------------+----------------+----------------+----------------+
| Approach | Strength | Weakness | Best when |
+------------------+----------------+----------------+----------------+
| Conservative | stable | slower | new design spin |
| Balanced | practical | needs monitoring | normal closure |
| Aggressive | fast | higher risk | schedule crunch |
| Structural | durable | long loop | repeat offender |
+------------------+----------------+----------------+----------------+When to choose each approach
Select strategy by risk budget, not convenience.
Interview traps
Skipping manifest diff
No side-effect regression
Evidence comparison
SYNTHESIS EVIDENCE MATRIX — Scenario: Retiming Debate
+--------------------+------------------------+--------------------------+-------------------------+
| Evidence | Tells you | Does not prove | Next action |
+--------------------+------------------------+--------------------------+-------------------------+
| compile QoR report | metric movement | root-cause class | inspect transform logs |
| SDC diff | constraint drift | library quality | rerun with baseline SDC |
| library map diff | cell view changes | RTL intent quality | lock/validate lib set |
| topo vs logical QoR | physical correlation | final route signoff | PD trial correlation |
| regression matrix | closure stability | architecture optimality | decide merge/rollback |
+--------------------+------------------------+--------------------------+-------------------------+Synthesis deep dive
Interview readiness comes from repeatable QoR reasoning under pressure.
Concept diagram
INTERVIEW ANSWER SHAPE
context -> metric -> mechanism -> fix -> regression -> ownershipMetric 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