Reset Deassertion CDC: Design Space

Design space exploration

For Reset Deassertion CDC, signoff options trade reliability, latency, and schedule.

Option A — conservative

• Conservative synchronization: helps robustness

• Risk: latency increase

• Validate with: stress regressions

Option B — balanced

• Balanced protocol design: helps throughput + safety

• Risk: higher design effort

• Validate with: formal + simulation

Option C — aggressive

• Aggressive waiver posture: helps schedule relief

• Risk: escape risk

• Validate with: periodic waiver audit

Option D — refactor

• Architectural refactor: helps long-term safety

• Risk: schedule hit

• Validate with: system bring-up

DESIGN SPACE — Reset Deassertion CDC
robustness <-> latency <-> complexity <-> schedule

Design pitfalls

• Waive-first behavior

• No owner for residual risk

Tradeoff curve

BEFORE / AFTER — Reset Deassertion CDC

open critical issues
  ^
  |  o baseline
  |     o after fix batch
  |         o after protocol proof
  |             o signoff-ready
  +---------------------------------> closure iteration

Track issue burn-down with evidence quality, not only count.

CDC/RDC deep dive

Reset release ordering is a first-order reliability contract.

Concept diagram

RESET RELEASE FLOW

assert global -> clocks stable -> sync release per domain -> first transaction

Metric graph

BOOT STABILITY

passes per 1k boots: 920 -> 980 -> 999

Reports and artifacts

• reset dependency matrix

• RDC warning classes

• boot stress logs

• waiver aging

Mini case study

Domain B released before producer A was valid, causing rare startup deadlock.

Debug branches

• Correlate reset and clock timelines

• verify async assert/sync release

• exercise skewed release tests

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

Asynchronous assertion is usually safe, but reset deassertion must be synchronized per destination domain to prevent uncertain startup state capture.

Metric: reset release violations, metastability-on-release risk, boot instability