I've noticed that at the simulation solver ramps up CPU usage then ramps down again in a regular cycle while iterating for a solution.
It will rarely use 100% of all 4 CPU's. It is better at using multi core Processors than it was in the past though.
The amount of multi-threading while solving a SOLIDWORKS Simulation study depends on many factors including study type, solver choice, and current solver task. It is normal to see CPU usage fluctuate between full usage of a single CPU core up to a maximum of full usage of all CPU cores. Full usage of all CPU cores (100% CPU Usage as reported in Task Manager) simultaneously is rare for FEA software.
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