How do you test a power-grid reservation against signal-routing capacity?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Overlay proposed ring, strap, rail, and via corridors on the same channel and congestion model used for signals, then compare remaining tracks and pin approaches.
Technical Explanation
Power and signals spend the same finite routing resources. Use current estimates, supply sources, macro PG pins, layer direction, width/pitch/spacing, via strategy, voltage-drop and EM targets as inputs; stop before full PG implementation or signoff.
Formula Or Decision Rule
Decision rule: accept the plan only if post-reservation signal capacity and PG feasibility both remain credible.
What To Check
• Warning sign: A clean signal map was produced before power corridors were reserved. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Add the planning reservation, rerun routing/pin checks, and revise the competing resource plan.
Command Checks & Actions
• check_design -checks {dp_pre_power_insertion}: runs named design-planning check groups
• report_congestion -mode summary: reports routing demand, capacity, overflow, or hot spots
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Overlay proposed ring, strap, rail, and via corridors on the same channel and congestion model used for signals, then compare remaining tracks and pin approaches. • Suspicious: A clean signal map was produced before power corridors were reserved. • Hard stop: required legality or physical feasibility is missing or unexplained. Add the planning reservation, rerun routing/pin checks, and revise the competing resource plan.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. A clean signal map was produced before power corridors were reserved.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you test a power-grid reservation against signal-routing capacity?” to measurable physical evidence and an owned correction.
Follow-up Question & Model Response
Follow-up probe: What would make you change your decision? Model response: “I would change it if the same controlled rerun shows that a clean signal map was produced before power corridors were reserved. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: A clean signal map was produced before power corridors were reserved. Corrective path: Add the planning reservation, rerun routing/pin checks, and revise the competing resource plan.
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