While Extreme speed can greatly decrease simulation run times, not all models are compatible with Extreme speed. When you start a simulation, Crystal Ball detects if the spreadsheet is compatible with Extreme speed and warns you if it is incompatible. If you choose, you can run the simulation in Normal speed using standard Microsoft Excel, or you can change the spreadsheet model to correct the incompatibility.
It is important to notice that incompatibilities in functions and formula constructs only concern the cells involved in the calculation of a forecast cell. If cells that are not part of that calculation path have incompatibilities, these are not detected and the simulation is allowed to run.