CDC Waiver Policy

What this topic teaches

CDC Waiver Policy focuses on closing CDC/RDC risk with mechanism-level reasoning. Waivers are controlled risk acceptances and must include mechanism justification, containment evidence, and ownership for periodic revalidation. Senior signoff depends on proving behavior with targeted evidence, not just clearing tool warnings.

The senior-engineer question

When open critical waivers, stale waiver age, waiver quality score regresses, can you classify the hazard, identify accountable owners, and choose the smallest fix or waiver backed by evidence?

CDC/RDC SIGNOFF FLOW — CDC Waiver Policy

crossing inventory + reset map
          |
          v
crossing classification (level/pulse/bus/reset)
          |
          v
structure + protocol + reset checks
          |
          v
critical issues + waiver review
          |
          v
fix / validate / regress / signoff

Picture the crossing behavior

Draw the behavior before touching tools. These visuals are the expected whiteboard baseline for reviews and interviews.

Waiver risk rubric

waiver request
   -> mechanism explanation
   -> containment evidence
   -> silicon-risk rating
   -> owner + expiry
   -> approve / reject

Crossing sequence

CROSSING FLOW — CDC Waiver Policy

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

Key metric: open critical waivers, stale waiver age, waiver quality score

Ownership layers

CDC/RDC OWNERSHIP LAYERS — CDC Waiver Policy

layer                 owns                            common failure
------------------    -----------------------------   -----------------------------
design intent         crossing architecture           wrong topology selected
protocol semantics    req/ack, fifo, ordering        liveness/deadlock bugs
reset behavior        assert/deassert sequencing      boot instability
analysis setup        tool rules + waivers            false confidence
signoff governance    risk acceptance + dashboard     stale critical waivers

Evidence to collect

• Primary metric: open critical waivers, stale waiver age, waiver quality score.

• Primary artifact: waiver template, risk rubric, waiver review minutes.

• Owners to involve: methodology owner, CDC lead, signoff manager.

• At least one reproducer tied to mode/reset/traffic context.

• Decision record: fix, waive, or escalate with rationale.

Ownership map

OWNERSHIP MAP — CDC Waiver Policy

artifact                  owner
----------------------    -------------------------
design intent           methodology owner
verification evidence   CDC lead
signoff decision        signoff manager

Every open CDC/RDC issue needs one accountable owner before waiver or fix.

Subpages in this topic

Each topic includes mechanism, I/O contract, metrics, debug, worked example, pitfalls, interview drills, checklist, theory, design tradeoffs, expanded case study, walkthrough, comparison matrix, software view, and silicon impact.

Key takeaways

• Classify crossing/reset hazards before proposing fixes.

• Pair structural results with protocol/reset behavioral proof.

• Treat waivers as bounded risk contracts, not cleanup shortcuts.

Common pitfalls

• Mass-waiving warnings near tapeout.

• Assuming local IP cleanliness guarantees SoC behavior.

• Skipping reconvergence and reset stress after CDC fixes.

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.