question

This question is explained in the CPU section of this Answers article: Companion to the Recommended Minimum System Requirements

CPU

Conventional wisdom dictates that better hardware will result in faster simulation runs. A single run of a FlexSim model is single threaded by definition (this differs when running experiments—more on that soon). For a single simulation run, increasing the core count of your processor won't do as much as increasing your processor's single core clock speed/efficiency. For the fastest individual model runs, you want the fastest processor possible, regardless of the number of cores.

When you're doing multiple model runs using the Experimenter or Optimizer, FlexSim takes advantage of multiple CPU cores. FlexSim will spawn as many instances as you have cores; for instance, a Quad core processor enables four single-threaded simulation runs to process simultaneously during a FlexSim experiment—one on each core. So if you are doing 100 replications, you'll get your results four times faster than you would by using a single core processor at the same speed/efficiency.

Conclusion: If you’re primarily doing single simulation runs, choose a faster processor speed regardless of the number of cores. If you’re primarily doing experiments, choose a processor with a high number of processing cores. If you’ll be doing both, choose a processor that strikes a good balance between core speed and core count.

Additional Note

FlexSim will use as much processing power as your computer will give it to run the simulation model, regardless of the model run speed.

This will not adversely affect the performance of other applications running on your computer. If other applications want processing power, then Windows will give it to them, and FlexSim will use less.

While FlexSim is running the model, the Windows task manager will show its usage at approximately 1 core of your processor. If you have a 1-core processor, it will show about 99%. If you have more cores, it will show a lower percent.

No matter how powerful your computer is, if you are running a FlexSim simulation model at unlimited speed, it will show max utilization of your cpu while the simulation model is executing.

Speeding Up a Simulation Model

Modifying how your model is designed will have more impact on how long it takes to run than increasing the power of your hardware.

This post has suggestions and links to other posts with suggestions that explain how to increase the performance of your FlexSim models: https://answers.flexsim.com/questions/25025/speeding-up-a-simulation-model.html