How do you calculate and round a core and die consistently?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Calculate ideal core dimensions, snap them to legal grids or row/site multiples, recompute actual area and utilisation, then add asymmetric offsets.
Technical Explanation
Rounding is a physical decision, not formatting. Illustrative: A = 960000 um^2, AR = 1.5 gives W = 1200 um and H = 800 um. With L/R/B/T = 60/90/50/70 um, die = 1350 um by 920 um before any required snapping.
Formula Or Decision Rule
W = sqrt(A x AR); H = sqrt(A / AR); die W = W+L+R; die H = H+B+T.
What To Check
• Warning sign: Rounded values are reported without recomputing actual area or occupancy. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Snap, recalculate, and place both ideal and final values in the review record.
Command Checks & Actions
• 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: Calculate ideal core dimensions, snap them to legal grids or row/site multiples, recompute actual area and utilisation, then add asymmetric offsets. • Suspicious: Rounded values are reported without recomputing actual area or occupancy. • Hard stop: required legality or physical feasibility is missing or unexplained. Snap, recalculate, and place both ideal and final values in the review record.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. Rounded values are reported without recomputing actual area or occupancy.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you calculate and round a core and die consistently?” 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 rounded values are reported without recomputing actual area or occupancy. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: Rounded values are reported without recomputing actual area or occupancy. Corrective path: Snap, recalculate, and place both ideal and final values in the review record.
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