Hi Abla,
We encountered this same issue here on a highly multi-core (48 logical cores) server when it was first installed for the lab.
You need to make sure that the Power Options in Windows show "High performance" and not "Balanced" or something else.
I was also told that there is a similar "maximum performance" setting in the UEFI/BIOS, and our IT group seemed to find it once I requested it, but I have not seen this myself.
In general, many computers actually run above what is listed as their "maximum speed" when they are fully loaded. So, a computer with a maximum speed of 2.1 GHz running at 1.2 GHz may be running at about 1/2 capacity.
We recently wrote a "Tip" page on system requirements for Skyline, which contains some of this information and more.
https://skyline.ms/wiki/home/software/Skyline/page.view?name=Skyline%20System%20Requirements
Hope this information helps. Good luck with getting the most out of your hardware with Skyline.
--Brendan