Which area categories must be separated before calculating a floorplan?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Separate standard-cell area, hard-macro area, fixed or physical-only cell area, placeable area, reserved area, and whitespace. Mixing them makes utilisation meaningless.
Technical Explanation
A single “total area” hides what can move, what consumes core space, and what must remain empty. Record the numerator and denominator for each metric. A macro-dominated block needs different reasoning from a standard-cell-dominated block.
Formula Or Decision Rule
Total occupied area = standard-cell area + counted macro area + other counted fixed/physical-only area.
What To Check
• Warning sign: A reported percentage cannot be reproduced because nobody knows which objects were counted. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Rebuild the area table from named object classes and use one declared convention for every alternative.
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: Separate standard-cell area, hard-macro area, fixed or physical-only cell area, placeable area, reserved area, and whitespace. Mixing them makes utilisation meaningless. • Suspicious: A reported percentage cannot be reproduced because nobody knows which objects were counted. • Hard stop: required legality or physical feasibility is missing or unexplained. Rebuild the area table from named object classes and use one declared convention for every alternative.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. A reported percentage cannot be reproduced because nobody knows which objects were counted.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “Which area categories must be separated before calculating a floorplan?” to measurable physical evidence and an owned correction.
Practical Example
Symptom: A reported percentage cannot be reproduced because nobody knows which objects were counted. Corrective path: Rebuild the area table from named object classes and use one declared convention for every alternative.
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