Ubuntu – ASUS UX533F temperature too high and fan off on Ubuntu 20.04 LTS

After installing Ubuntu 20.04 LTS, my laptop's temperature goes fairly high without intensive CPU activity. The fan(s) remain off under heavy CPU load and the temperature goes very high.

I don't suspect a material failure since I didn't have such overheating issues anymore with my previous Ubuntu (19.04).

EDIT: at the moment, after random attempts such as Uninstall/Reinstall the NVidia propietary driver, Downgrade/Upgrade the Linux kernel… The only issue left is sensors still sees the fan off (0 RPM) though I can hear it. No more overheating with my ASUS UX533F, hurray! but I don't know why so the problem might as well reappear some day…

Config

• ASUS UX533FN

• BIOS version 304 (up-to-date)

• Kernel: 5.4.0-31-generic (same issue with 5.4.0-29)

• NVIDIA GeForce MX150 (with latest NVIDIA driver)

Low CPU load

Without running anything special, I get the following figures with sensors command:

...
pch_cannonlake-virtual-0
Adapter: Virtual device
temp1:        +49.0°C  

BAT0-acpi-0
Adapter: ACPI interface
in0:          15.60 V  

asus-isa-0000
Adapter: ISA adapter
cpu_fan:        0 RPM

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +50.0°C  (high = +100.0°C, crit = +100.0°C)
Core 0:        +49.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:        +48.0°C  (high = +100.0°C, crit = +100.0°C)
Core 2:        +48.0°C  (high = +100.0°C, crit = +100.0°C)
Core 3:        +50.0°C  (high = +100.0°C, crit = +100.0°C)

acpitz-acpi-0
Adapter: ACPI interface
temp1:        +49.0°C  (crit = +103.0°C)

These figures are a too high in my opinion for low CPU load with a room temperature of 20°C.

But here come's worse:

Heavy CPU load

When the CPU is under load, for instance when running sysbench cpu run in loop, the temperature increases to 90°C, and no fan is triggered!

To get a repeatable CPU load test, I run

while true; do echo "One more time..." && sysbench cpu run; done

Here are the figures I get in this case (from sensors command):

...
pch_cannonlake-virtual-0
Adapter: Virtual device
temp1:        +65.0°C  

BAT0-acpi-0
Adapter: ACPI interface
in0:          15.60 V  

asus-isa-0000
Adapter: ISA adapter
cpu_fan:        0 RPM

coretemp-isa-0000
Adapter: ISA adapter
Package id 0:  +88.0°C  (high = +100.0°C, crit = +100.0°C)
Core 0:        +88.0°C  (high = +100.0°C, crit = +100.0°C)
Core 1:        +70.0°C  (high = +100.0°C, crit = +100.0°C)
Core 2:        +72.0°C  (high = +100.0°C, crit = +100.0°C)
Core 3:        +72.0°C  (high = +100.0°C, crit = +100.0°C)

acpitz-acpi-0
Adapter: ACPI interface
temp1:        +86.0°C  (crit = +103.0°C)

Note 1: The temperature in the room for this test is 20°C.

Note 2: I reported almost the same issue one year ago with Ubuntu 19.04.

What I already tried

• installing the latest NVIDIA driver, including selecting intel with prime-select ameliorated the situation but didn't tackle the issue

• running sensors-detect (YES to all questions) resulted in coretemp to be added to /etc/modules

• running pwmconfig didn't work:

/usr/sbin/pwmconfig: There are no pwm-capable sensor modules installed

How would you tackle this overheating issue?

Any help is appreciated.