Arch Linux

UliteXD

Member

Registered: 2026-05-18

Posts: 33

Linux ignoring AMI BIOS fan settings on Panasonic Toughbook CF-31

Hi, I have a Panasonic Toughbook CF-31, It has been giving me a lot of problems with drivers and sensors since I installed arch Linux on it. I have a lot of (minor) problems right now with the laptop (but I am too lazy to fix something like Bluetooth if I don't really use it) but one of the most concerning problems to me is cooling.

Hardware Modifications Attempted
I have done some physical modifications to the computer hoping to fix it like:

    replacing the thermal paste,

    cutting the case strategically to improve airflow,

    changing the fan,

    changing the whole heat sink,

I did all that because the laptop is almost 16 years old by now, so I figured might as well.) but none of those solved the issue (they helped, but they didn't solve it) the real issue here is not the hardware, but the software. The laptop chooses cooking itself to death rather than making noise with the fan.

I thought I could fix it in the bios, so I went in the bios and looked for something that I could tweak to modify the fan curve, but I only could find a setting called "Environment" which doesn't seem to do anything useful.

Then I thought (since the bios of this computer is kinda limited), the setting for the fan curve must be hidden, I extracted the bios, and looked at it with AMIBCP (I can't use Aptio V UEFI Editor since it only supports UEFI bioses and my bios is not UEFI) and I saw a lot of hidden options, something called debug mode in the bios had an option for fan curve in it, so I enabled it, and it works IN WINDOWS ONLY, so I have arrived at the conclusion that Linux is imposing it's own fan curve which is VERY BAD.

The Current (Problematic) Fan Curve
I say it is very bad because:

    From 50ºC downwards: The fan is completely off.

    At 51ºC: It starts at 30% speed, and it remains at 30% speed until temperature passes 75ºC.

    From 75ºC on: It goes 100% speed.

The problem is that the fan is able to cool a lot at 100% speed, so it goes to 75ºC scaling up, the fan speeds up and it starts really cooling, when it hits 90ºC the fan is able to bring the temp down (no thermal throttling is observed btw) to 74ºC or so, SO, the fan speeds down, and then the computer start overheating, at 90ºC again, so the fan speeds back up, and so on.

This considerably worries me because if this keeps happening I am going to end up breaking the computer.

So, what should I do to edit this fan curve? do you need any more details? something else I might have to try out?

Last edited by UliteXD (2026-06-07 21:49:49)

5hridhyan

Member

Registered: 2025-12-25

Posts: 822

Website

Re: Linux ignoring AMI BIOS fan settings on Panasonic Toughbook CF-31

a hunch, if it works on windows, then what happens if you spoofed it?
like

acpi_osi=\"Windows 2009\"

or w/ 2012 as https://wiki.archlinux.org/title/Kernel_parameters?
https://learn.microsoft.com/en-us/windo … inacpi-osi

UliteXD

Member

Registered: 2026-05-18

Posts: 33

Re: Linux ignoring AMI BIOS fan settings on Panasonic Toughbook CF-31

I tried but it didn't work unfortunately

5hridhyan

Member

Registered: 2025-12-25

Posts: 822

Website

Re: Linux ignoring AMI BIOS fan settings on Panasonic Toughbook CF-31

https://wiki.archlinux.org/title/Fan_speed_control...

UliteXD

Member

Registered: 2026-05-18

Posts: 33

Re: Linux ignoring AMI BIOS fan settings on Panasonic Toughbook CF-31

Yes, I saw that while looking for solutions, but Fancontrol does not detect any fans, NBFC does not have any profiles for my computer (maybe I could make one myself but I don't know how) and the rest are for specific laptops which are not mine, I did try them thou but as I expected, nothing changed. Maybe I am doing something wrong, but I don't think so.

Lone_Wolf

Administrator

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 15,065

Re: Linux ignoring AMI BIOS fan settings on Panasonic Toughbook CF-31

wall of text

Please add some line ends / paragraphs to make your posts (especially the first one of the thread) readable.

Moderator Note
Moving to Kernel & Hardware

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Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

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