Disable CPU Boost

There is a common way to do this, by limiting “Max CPU state” to 99%.
The flaw with this method is capping the CPU at only 1.7GHz.
To maintain stock 2.9/3.0GHz clock with boosting disabled, use this method below instead of 99% max power state.

1. Open regedit
2. Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power\PowerSettings\54533251-82be-4824-96c1-47b60b740d00\be337238-0d82-4146-a960-4f3749d470c7
3. Select Attributes and change it's value from 1 to 2. This will uncover a hidden power option.
4. After that, go back in the Power Plan Options and a new tab “Processor Performance Boost Mode” will appear. Set it to Disable and click Apply.
   Also, make sure your max processor state is at 100%. The CPU will now run on the stock frequency.
   

For a general idea about the performance compared to 99% max state, average FPS went up to about 5-15 with the temperatures still maxing out at the same 75 degree Celsius!
The FPS loss from 99% disabled has been recovered while maintaining the benefit! \\Tiering your games at 1.7GHz, 3.0GHz, and full boosting will allow greater flexible for performance and temperature. ”

Credits : Reddit

• In CMD as Administrator

 powercfg -attributes sub_processor perfboostmode -attrib_hide  

• Undo

 powercfg -attributes sub_processor perfboostmode +attrib_hide 

Control Panel → Power Options → Change Plan Settings → Change Advanced Power Settings → Processor Power Management → Processor Performance Boost Mode

While Disabled (Default: Aggressive) your thermals will improve drastically with minimal (CPU intensive games) or zero performance lost.
If you don’t want to completely disable it use Efficient Aggressive.