ExpertQuestion 10 of 10Source page 19

An engineer tells you "timing is clean." As the signoff lead, what do you ask before accepting that statement?

From PDVerse MMMC Interview Masterclass · pdVerse Mentor Series

Direct answer

Which modes, which corners, which setup views, which hold views, and were all the views required by the signoff plan actually active. Which libraries and RC/parasitic data were used, and how was variation (OCV/AOCV/POCV) and SI handled. Whether unconstrained paths were reviewed, exceptions validated, extraction is current, and whether any waivers are hiding underneath the headline result.

Mentor explanation

"Timing is clean" sounds like a finished statement, but on its own it's actually an incomplete sentence. Every one of those qualifiers — which modes, which corners, whether required coverage was actually active, what variation and SI settings were in effect, whether every path was even constrained in the first place — can be true or false independently of a clean-looking headline report. A design can show a green dashboard and still have an entire required view sitting inactive, an unconstrained path population nobody reviewed, or a stale SPEF nobody re-extracted. Asking these questions isn't distrust for its own sake — it's the actual definition of what "clean" is supposed to mean at signoff. "Timing clean" is a scoped statement about a specific, named set of conditions and checks — not an absolute property of the netlist.

Key takeaways

  • Which modes, which corners, which setup views, which hold views, and were all the views required by the signoff plan actually active.
  • Which libraries and RC/parasitic data were used, and how was variation (OCV/AOCV/POCV) and SI handled.
Visual explanationMMMC context: An engineer tells you "timing is clean." As the signoff lead, what…
MMMC context: An engineer tells you "timing is clean." As the signoff lead, what…A three-step concept map summarizes the focus, core answer, and practical verification for An engineer tells you "timing is clean." As the signoff lead, what do you ask before accepting that statement?Question focusAn engineer tells you"timing is clean." Asthe signoff lead, what…Core answerWhich modes, whichcorners, which setupviews, which hold views,and were…Verify in practiceValidate the configuredview, active objects,and report context.Understand → explain the mechanism → verify the assumptions
Self-check: can you answer this aloud?

Try a 45-second answer using this structure:

  1. State the direct answer.
  2. Explain the timing or physical reason.
  3. Name one caveat.
  4. Say how you would verify it in a real flow.

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