Boundary or corner cells are missing or wrongly oriented around a voltage area. What do you check?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Check voltage-area geometry, row orientation, inside versus outside corners, library-specific rules, legal cell orientations, and whether the correct insertion flow ran.
Technical Explanation
A missing cell may be a rule setup problem, a geometry problem, or a library availability problem. Do not substitute I/O corner, filler, tap, or decap cells. Use the correct core or voltage-area boundary family and rerun after geometry changes.
Formula Or Decision Rule
Decision rule: every applicable edge and corner has the intended cell and orientation.
What To Check
• Warning sign: A clean global count hides one untreated concave corner. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Report rules, inspect the named corner and rows, correct rule or geometry, compile, and check again.
Command Checks & Actions
• report_boundary_cell_rules: reports the active boundary-cell rules
• compile_boundary_cells -voltage_area <voltage_area>: inserts boundary cells using the active rules; this command is deprecated in the referenced release, so verify the project-approved targeted replacement
• check_floorplan_rules: reports configured floorplan-rule violations
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Check voltage-area geometry, row orientation, inside versus outside corners, library-specific rules, legal cell orientations, and whether the correct insertion flow ran. • Suspicious: A clean global count hides one untreated concave corner. • Hard stop: required legality or physical feasibility is missing or unexplained. Report rules, inspect the named corner and rows, correct rule or geometry, compile, and check again.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. A clean global count hides one untreated concave corner.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “Boundary or corner cells are missing or wrongly oriented around a voltage area. What do you check?” 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 global count hides one untreated concave corner. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: A clean global count hides one untreated concave corner. Corrective path: Report rules, inspect the named corner and rows, correct rule or geometry, compile, and check again.
Continue practising