Hello;
When i upgraded to windows 10 i found that my CPU 2.6GHz in the maximum , windows 7 was 3.0gHz.
Installed turbo-boost then i have done stress Test and i found only 2.63GHz 
- The power option High performance 100%
- Intel Corei7-3517U CPU @ 1.90GHz
- Dell inspiron 5521