What evidence makes an initial floorplan reviewable?
From PDVerse PnR Interview Handbook, part of the pdVerse Mentor Guide
Short Answer
A screenshot of a floorplan tells you what it looks like, not whether it's actually sound — real reviewability comes from reports and saved constraints that show what the tool actually understands, not what the picture visually suggests. A reviewable floorplan has to demonstrate, with evidence: deliberate (not accidental) boundaries, a stated utilization number, genuinely usable rows, macro locations with a justification (not just "it fit there"), feasible routing channels, properly constrained pins, early congestion/timing evidence, reserved PG resources, voltage-area legality, and — critically — reproducible write-out (someone else can regenerate your evidence from the same inputs).
Technical Explanation
- Legality and quality are two completely separate axes, and conflating them is a common mistake — a floorplan can pass every hard legality check and still be a poor-quality floorplan with bad congestion, weak timing margin, or high downstream change risk.
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- Practically, this means a review package should include: utilization/density reports, row/legality checks, macro placement rationale, early global-route congestion output, port/pin constraint verification, PG reservation confirmation, and a documented list of known risks — not just a rendered picture of the layout.
Formula Or Decision Rule
Decision rule: proceed only when hard stops are closed and remaining risks have evidence, owners, and review dates.
What To Check
- Warning sign: The floorplan looks tidy but cannot be reproduced or has unexplained warnings.
- Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause.
- Correct: Reopen the saved checkpoint, rerun the evidence package, and record the proceed/iterate decision.
Command Checks & Actions
report_design-floorplan: reports the floorplan state understood by the toolcheck_design-checks {dp_pre_macro_placement dp_pre_power_insertion dp_pre_pin_placement dp_floorplan_rules}: runs named design-planning check groupswrite_floorplan-output <output_dir>: writes reproducible floorplan information to files
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.
Healthy, Suspicious & Hard-stop Results
- Healthy: A reviewable floorplan has deliberate boundaries, utilisation, usable rows, justified macro locations, feasible channels, constrained pins, early congestion/timing evidence, PG reservation, voltage-area legality, classified findings, and reproducible write-out.
- Hard stop: required legality or physical feasibility is missing or unexplained.
Common Mistake
The Trap: Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change.
What The Interviewer Is Testing
” to measurable physical evidence and an owned correction.
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