How do you test whether ICC2 and PrimeTime use different libraries?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Compare resolved library versions, PVT, operating conditions, cell identities, and scenario mapping before path arithmetic.
Technical Explanation
When two tools disagree, compare the inputs and analysis context before comparing slack. Units, libraries, PVT, clocks, exceptions, and modes must line up first.
What To Check
• Warning sign: The same instance has materially different cell delay in the two tools. • Inspect: Keep at least two possible causes open, then use one named object and the active mode or scenario to separate them. • Correct: Align the approved model sets and contexts through the library/STA owners, then compare one fully expanded path.
Command Checks & Actions
• report_ref_libs: shows the reference libraries used for linking
• report_pvt: shows process, voltage, and temperature assignments
• report_scenarios: shows the MCMM scenario matrix and analysis status
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: Compare resolved library versions, PVT, operating conditions, cell identities, and scenario mapping before path arithmetic. • Investigate: The same instance has materially different cell delay in the two tools. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Align the approved model sets and contexts through the library/STA owners, then compare one fully expanded path.
Common Mistake
Do not assume the check passed just because ICC2 continued: The same instance has materially different cell delay in the two tools. Fix or narrowly justify the named objects, then rerun the same command.
What The Interviewer Is Testing
Be ready to explain why this matters before floorplanning: The same instance has materially different cell delay in the two tools.
Follow-up Question & Model Response
Model response: “I would save the report, inspect one affected object in the correct block and scenario, and make or request this correction: Align the approved model sets and contexts through the library/STA owners, then compare one fully expanded path. Then I would reopen the clean checkpoint and rerun the same evidence.”
Practical Example
Symptom: The same instance has materially different cell delay in the two tools. Corrective path: Align the approved model sets and contexts through the library/STA owners, then compare one fully expanded path.
Continue practising