Comment 5 for bug 2054921

please try to customize the fan curve by editing the /boot/firmware/config.txt file
you can do it by adding something like this:

```
dtparam=fan_temp0=65000
dtparam=fan_temp0_hyst=2500
dtparam=fan_temp0_speed=75

dtparam=fan_temp1=70000
dtparam=fan_temp1_hyst=2500
dtparam=fan_temp1_speed=128

dtparam=fan_temp2=75000
dtparam=fan_temp2_hyst=2500
dtparam=fan_temp2_speed=192

dtparam=fan_temp3=80000
dtparam=fan_temp3_hyst=2500
dtparam=fan_temp3_speed=255
```

This tells the system to start the fan once the temp reaches 65°C not before,
at 70°C it increases the fan speed, at 75°C it increases it even more until 80°C when the fan spins at 100%.

This configuration is completely ignored with the current bcm2712-rpi-5-b.dtb file, you can see that the fan starts at 50°C and not at 65°C.

Now try to overwrite that file with this one:
https://github.com/raspberrypi/firmware/blob/master/boot/bcm2712-rpi-5-b.dtb
reboot the system and try again and boom, it now works as expected.

To stress the CPU and monitor the CPU temperature/Fan speed at the same time, you can use a tool like s-tui.
https://github.com/amanusk/s-tui

feel free to ask if you need further info :)
thanks
Davide