How do you debug rows created with the wrong site?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Compare row site names, library cell site compatibility, row height/width, orientation, voltage area, and the intended row pattern.
Technical Explanation
A row can exist while no intended cell can legally use it. Inspect one failing cell and one row. The site relationship should explain the legality failure directly.
Formula Or Decision Rule
Decision rule: the site used by each row must support the cells assigned to that row class.
What To Check
• Warning sign: Cells remain unplaceable or multiple-height cells have no compatible rows. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Recreate affected rows or site arrays from the approved library definitions, then recheck.
Command Checks & Actions
• create_site_row -name <row> -site <site> -origin {<x> <y>} -site_count <count>: creates one named row from a site and origin
• report_design -floorplan: reports the floorplan state understood by the tool
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Compare row site names, library cell site compatibility, row height/width, orientation, voltage area, and the intended row pattern. • Suspicious: Cells remain unplaceable or multiple-height cells have no compatible rows. • Hard stop: required legality or physical feasibility is missing or unexplained. Recreate affected rows or site arrays from the approved library definitions, then recheck.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. Cells remain unplaceable or multiple-height cells have no compatible rows.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you debug rows created with the wrong site?” 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 cells remain unplaceable or multiple-height cells have no compatible rows. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: Cells remain unplaceable or multiple-height cells have no compatible rows. Corrective path: Recreate affected rows or site arrays from the approved library definitions, then recheck.
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