FEMAP does not use the GPU for processing, however it sounds as if your question may be more related to Nastran than to FEMAP.
When you launch an analysis from FEMAP, the analysis is run in a separate process. Assuming you're using Nastran, that will show up in the Windows Task Manager as "analysis.exe". That's the process you'll want to observe to see how much CPU is being utilized during an analysis.
There's a couple of other things you should keep in mind when trying to determine how much of your computer is being used to to run an analysis. First, Windows reports CPU utilization percentage as a total based on the number of cores your machine has. If, for example, your machine has an 8 core CPU, if only a single core is being used, the percentage of CPU utilization for that process will not go above 12%. Additionally, CPU usage alone may not be an good indicator of if your model is actively being analyzed. Depending on the model as well as the solution sequence, there the analysis may be very disk I/O intensive rather than CPU intensive. If this is the case, you may see more activity in the I/O columns in the analysis manager and relatively little activity in the CPU column.
Regarding your solution time of 2-3 minutes, depending on the model and the analysis, that may not be unreasonable. If you would like to post more information about your model (number of nodes, number of elements, topologies used, solution sequence, etc) as well as information regarding your machine (processor, amount of RAM, hard drive info) I could try to provide some guidance.