CDC Review Gate: Silicon PPA Impact

Silicon PPA and reliability impact

Signoff dashboards keep risk visible across milestones.

Area drivers

• extra synchronizer stages

• FIFO buffering

• diagnostic observability logic

Power drivers

• additional flops

• always-on reset logic

• debug monitors

Timing/latency impact

• added latency through synchronizers

• pointer synchronization delays

PD consequences

• placement proximity of sync stages

• clock/reset tree interactions

Verification burden

• formal liveness reruns

• stress simulation matrix

PPA / RELIABILITY — CDC Review Gate
area/power/latency vs reliability margin

Key takeaways

• Reliability has implementation cost

• Track that cost explicitly in signoff decisions

Design option reliability curve

METASTABILITY ENVELOPE — CDC Review Gate

probability of unresolved state
  ^
  |\
  | \
  |  \
  |   \
  +------------------------------> settle time
      short settle      long settle

Design lever: more settle time and correct synchronizer topology increase MTBF.

CDC/RDC deep dive

Signoff is an evidence governance problem across teams.

Concept diagram

CDC SIGNOFF LOOP

analysis -> triage -> fix/waive -> review gate -> dashboard

Metric graph

CRITICAL OPEN COUNT

week1 34
week2 22
week3 10
week4 0

Reports and artifacts

• critical by owner

• waiver quality

• review gate status

• closure trend

Mini case study

Pass rates improved while critical waivers aged out of policy; dashboard exposed hidden risk.

Debug branches

• Separate quality from quantity metrics

• enforce waiver expiry

• run gate checklists consistently

Senior review question

Ask: what evidence proves this risk is closed for silicon, not just tool-clean?

Key takeaways

• State crossing class, assumptions, and owner with every issue.

• Run structural and dynamic regressions after each fix.

Common pitfalls

• Treating all warnings as equivalent risk.

• Waiving issues without containment evidence.

• Skipping reset and reconvergence stress after CDC fixes.

Principal CDC/RDC review addendum

Gate reviews align RTL, verification, and signoff evidence before integration milestones to avoid endgame metastability surprises.

Metric: gate pass rate, late-stage CDC churn, review defect leakage