My PC is a Toshiba satellite L55 with an Intel core i5 running windows 10, and the maximum clock speed is 2.4GHz. It has been running good and the clock speed used to increase with the usage percentage, but now the clock speed is constant (mostly at 2.74GHz) but the usage percentage lowers and increases depending on what I am doing. I tried booting it in safe mood but no change at all, and it's running on a SSD if that's important.
The path might be slightly off since i'm doing this via a win8.1 device, but the idea stays the same:
Control Panel > All Control Panel Items > Power Options and click on
Change plan settings for your current power plan.
Change advanced power settings and go to the
Processor power management. In there you can have a look at the
Minimum processor state setting.