I have one idea. The temperture. While the CPUs Tjunction is set to 100c, meaning it will operate at up to 100c, the laptop maker probably set their safe guard at a lower temperature.
When the CPU reaches that temperature, it will downclock itself according to the BIOS till it reaches that temperature or lower.
I would suggest getting a decent cooling pad for it for when you play games. There are some nice ones with big 200mm fans that will help cool it down.
That or get a desktop for gaming as laptops are not well suited for it, even when they are designed for it. I am not a laptop fan due to them shoving extremley hot components into a small space with inadequate cooling.