A macro is inside the core but off-grid or illegally oriented. Is this a minor warning?
From PDVerse PnR Interview Handbook, part of the pdVerse Mentor Guide
Short Answer
No — this is not a minor warning, and treating it as one is a common but costly mistake. "Inside the core boundary" tells you nothing about whether the macro is sitting on a legal manufacturing/block-grid coordinate. An off-grid or illegally-oriented macro can break several things at once: manufacturing/block-grid requirements, pin access, array-alignment relationships with neighboring instances, and power connectivity — any one of which is a signoff blocker on its own.
Technical Explanation
- Treat this as a hard stop for that specific macro placement, not something to fix "later in the flow" — problems like this tend to compound (routes get built against the illegal position, then have to be redone) the longer they sit unresolved.
- Full verification means checking allowed orientation, the applicable alignment grid and alignment point, the macro's origin, its dimensions, which sides carry pins, its power-pin locations, and — if it's instantiated multiple times — consistency across those instances.
- This mirrors the macro-grid-alignment question in this set: don't let a clean-looking outline substitute for actually verifying every legality dimension.
Formula Or Decision Rule
Decision rule: the final transformed macro satisfies every applicable legality and interface condition.
What To Check
- Warning sign: The macro is manually nudged until one warning disappears.
- Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause.
- Correct: Apply the approved constraints, snap deliberately, and rerun macro and floorplan-rule checks.
Command Checks & Actions
- set_macro_constraints -allowed_orientations <orientation_list> -alignment_grid <grid_name> <macro_collection>: records allowed macro or I/O placement constraints
check_design-checks {dp_pre_macro_placement}: runs named design-planning check groups- 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: No. It can break manufacturing/block-grid requirements, pin access, array alignment, or power connectivity; treat it as a hard stop for that macro placement.
- 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
The interviewer is testing whether you can connect “A macro is inside the core but off-grid or illegally oriented. ” to measurable physical evidence and an owned correction.
Follow-up Question & Model Response
"* Candidate Model Response: Model response: “I would change it if the same controlled rerun shows that the macro is manually nudged until one warning disappears. ”
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