CDC / RDC · All levels

Scenario: Metastability Bug: Comparison Matrix

Comparison Matrix for Scenario: Metastability Bug.

Comparison matrix

Interview responses must balance depth, clarity, and tradeoff judgment.

diagram

+------------------+----------------+----------------+----------------+
| Approach         | Strength       | Weakness       | Best when      |
+------------------+----------------+----------------+----------------+
| Conservative     | safe           | extra latency  | high-risk crossings |
| Balanced         | practical      | more setup     | most production paths |
| Aggressive       | fast schedule  | escape risk    | late-stage crunch |
| Refactor         | structural gain | long cycle     | recurring failures |
+------------------+----------------+----------------+----------------+

When to choose each approach

Select approach by silicon risk, not only schedule urgency

Interview traps

Global waiver spray
Unproven protocol assumptions

Evidence comparison

diagram

CDC/RDC EVIDENCE MATRIX — Scenario: Metastability Bug

+-----------------------+----------------------------+----------------------------+---------------------------+
| Evidence              | Tells you                  | Does not prove             | Next action               |
+-----------------------+----------------------------+----------------------------+---------------------------+
| structural report     | crossing topology class    | protocol liveness          | add assertions/formal     |
| reset map             | release dependencies       | dynamic startup behavior   | run reset stress tests    |
| formal proof          | bounded safety/liveness    | real firmware sequence     | correlate with simulation |
| simulation stress     | observed mode behavior     | full state-space closure   | target unhit corners      |
| waiver log            | accepted residual risk     | technical correctness      | periodic revalidation     |
+-----------------------+----------------------------+----------------------------+---------------------------+

Scenario debrief

Score each response on mechanism clarity, evidence quality, and signoff decision discipline.

diagram

INTERVIEW FLOW

classify -> explain mechanism -> propose fix -> state regression

diagram

PRACTICE SCORE

session1 62%
session2 78%
session3 89%

Debrief prompts

Which crossing class or reset dependency failed first?
What evidence changed your decision?
Fix, waive, or escalate and why?

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.

Practice this lesson