How do target, effective, and local utilisation differ?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Target utilisation is an input assumption; effective utilisation is the achieved counted occupancy after exclusions; local utilisation measures a smaller region. They answer different questions.
Technical Explanation
A city can have open land overall while one neighbourhood is full. Local utilisation exposes that floorplan problem. Always compare values with the same object classes, exclusions, and region definition. Blockages, voltage areas, halos, and fragmented rows change usable capacity.
Formula Or Decision Rule
Local utilisation = counted area inside region / usable placeable area inside the same region.
What To Check
• Warning sign: Average utilisation looks healthy while cells are trapped beside a macro or voltage-area boundary. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Measure the failing region, remove the cause of fragmentation or redistribute demand, then recompute.
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: Target utilisation is an input assumption; effective utilisation is the achieved counted occupancy after exclusions; local utilisation measures a smaller region. They answer different questions. • Suspicious: Average utilisation looks healthy while cells are trapped beside a macro or voltage-area boundary. • Hard stop: required legality or physical feasibility is missing or unexplained. Measure the failing region, remove the cause of fragmentation or redistribute demand, then recompute.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. Average utilisation looks healthy while cells are trapped beside a macro or voltage-area boundary.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do target, effective, and local utilisation differ?” to measurable physical evidence and an owned correction.
Practical Example
Symptom: Average utilisation looks healthy while cells are trapped beside a macro or voltage-area boundary. Corrective path: Measure the failing region, remove the cause of fragmentation or redistribute demand, then recompute.
Continue practising