There seems to be an issue with the Intel Core i7-8550U (Datasheet) which are built into Lenovo Laptops. The Problem:
In Windows the CPU does not clock over like 40-80 % of the base frequency. The value seems to be related to the specific CPU und not to software. It will stay in that range for all the time running Windows. What we found out:
The issue seems not to be related to a single Laptop. It is occuring on my personal ThinkPad E580 and on a friends ThinkPad E480 with the same CPU. The issue is only occuring on Windows (10 so far, not tested other versions). On Linux the CPU is clocking without a Problem to clock speeds up to 4GHz which is the turbo frequency (Tried Ubuntu and Fedora). Heat is also not an issue when using Windows, since the fans are barely spinning. All the drivers are up to date and the bios is on the newest version. The Windows energy settings are also set to full power and CPU frequency. It occurs on battery and plugged in.
Steps to fix the issue short term:
The only way we discovered to fix this issue is by installing ThrottleStop and playing around with the parameters until the CPU seems to clock with a max speed of around 180% base frequency. Can anyone confirm this issue with a Lenovo Laptop and an i7-8550U with the up to date bios (or any other configuration with this CPU)? Speculations
Until this problem only occurs on Windows there seems to be a Windows driver issue (?) or in the way windows handles the CPU throttling at all. Could it be possible that there is a value set in the CPU config/bios that Windows reads and uses but Linux ignores?
Btw, we are also in contact with the Lenovo Customer Support but that seems to take while.
