This is most certainly a check against either virtualization or the presence of a debugger observing the process. If the maximum performance of the core you're

This is most certainly a check against either virtualization or the presence of a debugger observing the process. If the maximum performance of the core you're running on varies significantly over time, chances are that your process isn't running on its own in an OS running on bare metal and the extra layers give an attacker a chance to observe and reverse engineer the checks.