CDC Review Gate: Expanded Case Study

Extended case study

Milestone review flags gate pass rate, late-stage CDC churn, review defect leakage around CDC Review Gate.

Background

Team believed crossings were stable until stress mode exposed intermittent anomalies.

Symptoms observed

• gate pass rate, late-stage CDC churn, review defect leakage regression

• Mismatch between structural report and dynamic behavior

• Waiver debate under schedule pressure

Investigation timeline

1. Freeze design, reset, and tool configuration tags.

2. Reproduce failing scenario with minimized stimulus.

3. Map path/protocol/reset dependencies.

4. Classify root cause and containment options.

5. Execute minimal safe fix.

6. Run stress regression and review board.

Root cause

Root cause links to CDC Review Gate: Gate reviews align RTL, verification, and signoff evidence before integration milestones to avoid endgame metastability surprises.

Fix and validation

• Targeted RTL/protocol/reset correction

• Evidence refresh

• Signoff board decision

Lessons learned

• Treat waivers as temporary risk contracts

• Track owner and expiry

• Regression before closure

CASE STUDY — CDC Review Gate
critical issues before / after / signoff

Crossing sequence under stress

CROSSING FLOW — CDC Review Gate

source clock domain -> launch signal -> crossing structure -> destination sample
      |                    |                 |                    |
   source FF           protocol           sync / fifo         destination FF

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

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