DELL xps 9560 bad performances

I'm using ubuntu 22.04 and I have a strange issue, the I7-7700HQ frequency is inversely proportional to cpu load, for example, when I run :

stress-ng -c 8

or

7z b

the frequency drops to 800MHz on all cores. However when the computer is in IDLE, the frequency is at the base frequency (2800MHz here). Another problem is that I never successfully get a frequency above the base frequency, up to turbo frequency (3800MHz).

What I tried :

• disable, reboot, then re-enable turbo-boost in BIOS, it set the no_turbo statement to 0.
• add intel_pstate=enable to GRUB_CMDLINE_LINUX_DEFAULT in grub configuration (without forgetting to run update-grub).
• use cpupower command line and gui tool, it doesn't have any effect and it's not permanent at reboot.

useful information :

$ sensors
...

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +42.0°C  (high = +100.0°C, crit = +100.0°C)
Core 0:        +42.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:        +42.0°C  (high = +100.0°C, crit = +100.0°C)
Core 2:        +41.0°C  (high = +100.0°C, crit = +100.0°C)
Core 3:        +41.0°C  (high = +100.0°C, crit = +100.0°C)

...

while I typed this command I was running 7zip benchmark, as you can see, the CPU stays very cold, the frequency was 800MHz on each core.

$ cat /sys/devices/system/cpu/intel_pstate/no_turbo
0
$ cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
performance
performance
performance
performance
performance
performance
performance
performance
$ cat /sys/devices/system/cpu/intel_pstate/status
active

NOTE : scaling_governor is set to performance by cpupower-gui, but it has no effect and go back to powersave at reboot.

This laptop is very silent, sometimes the fans even stop running, but for a I7-7700HQ the performances are very weak, even internet browsing with web app is slow. Even my 2012 AMD FX6300 have better performances than this 2017 laptop...

My battery is in correct condition and during all those tests I was on the 130W AC adapter (correctly detected by the BIOS).

Thank by advance for your answers

PS : sorry for my English ()

So, finally the issue was what I mentioned in my comment : due to an previous overheating, the laptop was locked in a sort of "failsafe mode" where the frequency is limited to 800MHz.

After removing the battery for 10 minutes then reconnect it the frequency go back to normal, by a variation between 900 and 3800MHz, in function of the load. Now it's perfectly fluid !