question

Modern computers have multiple cores and some are able to process in one core two threads. Each Experiment scenario or instance can run in an own thread and / or processor core. BUT most computers are still lacking of having enough RAM to execute parallel on all cores your Modell Runs. The Windows system starts to store processing data and execution code from RAM and cache memory to a slow storage space on a hard drive (hdd or ssd). Later when needed your system read this data. This virtual memory on a disk is much more slower, I mean really really slow in comparison to RAM.

You can limit the number of threads and processor cores in Experimenter advanced settings. Then you can watch how your system efficiency is in task manager efficiency viewer. I would start in experimenter advanced setting with one core and watch the free memory in your system while Modell run. Only if there isn’t stored any data in virtual memory you can add another processor core in experimenter to your runs.