Elitebook 840 G5 very slow CPU performance

[lamer305]

Hi,

the CPU (Core i7 8650U) of my Elitebook 840 G5 runs on a maximum frequency of around 1 GHz, and while on battery at approx. 600 Mhz only. Everything feels very, very slow, even simple things like opening a browser or starting and using any of the pre-installed windows programs. The notebook is equipped with 16 GByte RAM and a 2 TB SSD. The root cause is definitely the CPU, which does not over 1 GHz.

I did a fresh installation of the latest version of Windows 10 EE and afterwards a fresh installation Windows 11 with all the latest drivers, and the BIOS has also been updated to the most current version, BIOS settings have been reset to their defaults etc., but the problem remains the same. 

Any ideas would be highly appreciated. Thanks!

[lamer305]

... in the meantime I have also checked it with the latest version of Ubuntu Linux. The CPU is running at exactly 1000 MHz maximum, even under stress. So it´s not a Windows/driver specific  issue. 

Any ideas?

[lamer305]

Finally I found out that the problem occurs only when the battery is physically connected to the motherboard. If I disconnect the battery, the CPU runs perfectly on the designated frequency (around 2 GHz).

However, I replaced the battery with a new one, and unfortunately the problem is the same. So again, if a battery is physically connected to the motherboard of the laptop, the CPU runs at a maximum frequency of around 1 GHz while on AC, and at a maximum speed at around 600 MHz while on battery.

Could this be a physical issue with the motherboard (which can only be solved with a replacement), or is a bug of the BIOS more likely?