Problem with using both CPUs

Hi,

I have recently bought a workstation with two Xeon Gold CPUs each having 16 cores (expecting to speed up the simulation!). When I use only one CPU and 16 cores (by going to Preferences>Multicore and cluster computing), the computational time is 43 seconds and 32% is utilized during simulation. However, when I choose to use both sockets and all cores, the computational time rises to 47 seconds while utilization rate of CPU is 65% during the simulation!!

I would appreciate if someone could help me with this incosistency.