MCMM (multi-mode multi-corner)
Beginner
Checking the chip in every way it will be used, in every place it will be.
Novice
Checking timing in every scenario. A scenario combines a mode (a way the chip is used, such as normal operation or test) with a corner (a combination of manufacturing extreme, voltage and temperature). Timing must pass in all of them.
Expert
Each scenario pairs a mode (its own SDC constraints) with a PVT corner (Liberty) and an RC corner (SPEF). The raw count is modes × PVT corners × RC corners; teams prune scenarios that never set the worst slack anywhere. Optimization and ECO tools load many scenarios at once so a fix in one doesn’t break another.