I have just upgraded and activated my ThinkPad X201 Tablet PC (i7 L640 @2.13 GHz, 4GB DDR3 RAM) to Windows 10 Pro (64-bit) from the original Windows 7 Pro (64-bit). The tablet appears to run fine in Windows 10 Pro. However, the Task Manager's Performance tab page shows the CPU run at the frequency between 1.17 and 1.20 GHz, even as the tablet takes several tasks and runs at 60% and above and the tablet's power mode is set to high-performance.

What went wrong? What are the things that I need to check? Please advise.