How does a macro halo differ from a placement blockage?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
A keepout margin moves with its macro; a placement blockage is a fixed floorplan region. Both reserve space, but ownership and affected objects differ.
Technical Explanation
A halo is a personal buffer around furniture; a blockage is a “do not place” zone painted on the floor. Hard, soft, hard-macro, partial, and routing-related restrictions must be chosen for the intended object type and stage.
Formula Or Decision Rule
Decision rule: reserve only the space needed for pin access, routing, optimisation cells, or physical rules, and state what the restriction blocks.
What To Check
• Warning sign: A huge halo wastes rows, or a small halo allows cells to choke macro pins. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Adjust the specific keepout or blockage based on evidence and compare usable rows and congestion again.
Command Checks & Actions
• create_keepout_margin -type hard -outer {<left> <bottom> <right> <top>} <macro_collection>: attaches a typed keepout margin to design objects
• create_placement_blockage -boundary {{<llx> <lly>} {<urx> <ury>}} -type hard -name <blockage>: creates a fixed placement restriction
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 keepout margin moves with its macro; a placement blockage is a fixed floorplan region. Both reserve space, but ownership and affected objects differ. • Suspicious: A huge halo wastes rows, or a small halo allows cells to choke macro pins. • Hard stop: required legality or physical feasibility is missing or unexplained. Adjust the specific keepout or blockage based on evidence and compare usable rows and congestion again.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. A huge halo wastes rows, or a small halo allows cells to choke macro pins.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How does a macro halo differ from a placement blockage?” to measurable physical evidence and an owned correction.
Practical Example
Symptom: A huge halo wastes rows, or a small halo allows cells to choke macro pins. Corrective path: Adjust the specific keepout or blockage based on evidence and compare usable rows and congestion again.
Continue practising