Congestion becomes severe only after PG-resource reservation. What does that prove?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
It proves the earlier signal-only model was incomplete, not that power planning should be ignored. Rebalance shared routing resources and floorplan geometry.
Technical Explanation
Power and signal feasibility must coexist in one plan. Compare layers, directions, macro pin escapes, channel width, via corridors, and local demand with the reservation present. Verify the PG assumptions are themselves approved.
Formula Or Decision Rule
Decision rule: no floorplan passes on a model that omits required power resources.
What To Check
• Warning sign: The team reports the earlier prettier map. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Keep the correct reservation, fix the shared-resource conflict, and archive both maps as evidence.
Command Checks & Actions
• check_design -checks {dp_pre_power_insertion}: runs named design-planning check groups
• report_congestion -mode hot_spot: 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: It proves the earlier signal-only model was incomplete, not that power planning should be ignored. Rebalance shared routing resources and floorplan geometry. • Suspicious: The team reports the earlier prettier map. • Hard stop: required legality or physical feasibility is missing or unexplained. Keep the correct reservation, fix the shared-resource conflict, and archive both maps as evidence.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. The team reports the earlier prettier map.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “Congestion becomes severe only after PG-resource reservation. What does that prove?” 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 the team reports the earlier prettier map. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: The team reports the earlier prettier map. Corrective path: Keep the correct reservation, fix the shared-resource conflict, and archive both maps as evidence.
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