How do you interpret feedthrough reports?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Classify original, created, buffered, reused, redundant, unused, pure, and mixed feedthroughs; then inspect the nets whose classification conflicts with intent.
Technical Explanation
Counts are a starting point. Names and physical paths reveal whether the block interface is healthy. A reused feedthrough may be efficient, while an unused or redundant one may waste pins. Buffering can help timing but changes block ownership and power needs.
Formula Or Decision Rule
Decision rule: every feedthrough has a functional reason, legal pin pair, route opportunity, and owner.
What To Check
• Warning sign: A clean total hides one redundant path or an unused pin pair. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Report targeted classes, inspect named nets, remove or repair the cause, and rerun.
Command Checks & Actions
• check_feedthroughs -unused_feedthroughs -reused_feedthroughs -redundant: checks targeted feedthrough classes and constraints
• report_feedthroughs -include_buffered -reporting_style net_based: reports feedthrough nets and traversed blocks
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Classify original, created, buffered, reused, redundant, unused, pure, and mixed feedthroughs; then inspect the nets whose classification conflicts with intent. • Suspicious: A clean total hides one redundant path or an unused pin pair. • Hard stop: required legality or physical feasibility is missing or unexplained. Report targeted classes, inspect named nets, remove or repair the cause, and rerun.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. A clean total hides one redundant path or an unused pin pair.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you interpret feedthrough reports?” 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 total hides one redundant path or an unused pin pair. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: A clean total hides one redundant path or an unused pin pair. Corrective path: Report targeted classes, inspect named nets, remove or repair the cause, and rerun.
Continue practising