# How to deactivate a temp sensor or change the temp limit?



## Xosted (Mar 24, 2011)

Hi,

There is a temperature sensor on the motherboard of my system which seems not to work properly. It affects this value

```
hw.acpi.thermal.tz0.temperature: 50.0C
```

Thanks to external sensors, I know that the given value is always 15 to 20 degrees above reality. As a consequence, when I run heavy processes (or just try to build "FreeBSD's world") the system reaches the limit, emits a warning and shuts down.

So how do I deactivate this sensor so FreeBSD doesn't react to it at all? Or at least, how can I change the temperature limit so it is not that easily reached?

Thank you.


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## SirDice (Mar 24, 2011)

Are you sure it's FreeBSD that's shutting the machine down? If so it's shutdown cleanly. It can however also be the BIOS and when that shutsdown the machine it'll be hard. A clean shutdown will mark your filesystems clean and doesn't need to fsck when it's started again. A hard shutdown leaves the filesystems dirty and thus requires an fsck.

The BIOS temperature limits are obviously set in the BIOS :e


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## Xosted (Mar 24, 2011)

Hi,

No doubt that it is FreeBSD. Everything is clean. Furthermore, if it was the BIOS, it wouldn't have the politeness to warn so there would be no message announcing the shutdown.


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## rdeiriar (Apr 3, 2011)

Xosted said:
			
		

> Hi,
> 
> No doubt that it is FreeBSD. Everything is clean. Furthermore, if it was the BIOS, it wouldn't have the politeness to warn so there would be no message announcing the shutdown.



Not Necessarily. The BIOS could send an ACPI shutdown signal to the OS. FreeBSD would then shut down cleanly.


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## Xosted (Jul 30, 2011)

Hi,

I know it has been a long time but this issue is still not solved.
The problem is still the same, the computer shuts down as soon as the M/B sensor reaches 60 degrees.

So far, I could not find any reason for this to happen. On FreeBSD side, I'm told that it is the BIOS sending a shutdown message. On hardware forums, it is FreeBSD which is suspected to shutdown by itself....

So, is there any such thing, in FreeBSD, that monitors temperatures and initiates shutdown upon reaching a limit?
Is there anyways to modify such limit?
Is there anyways to instruct FreeBSD to ignore a message from the BIOS?


As well:
I turned on the computer and entered the BIOS. There, after setting the fans to the minimal rotation, I watch the temperatures rising. They went above 65 degrees and it didn't shutdown. The same experiment within FreeBSD with "healthd -d" launched to observe temperatures, got the computer to shutdown as soon as the first temperature displayed reached 60 degrees.
Is the BIOS sending messages to the operating system, but not applying them itself?


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## Crest (Jul 31, 2011)

Afaik the ACPI implementation generates events for devd. Check your devd config files.


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## Terry_Kennedy (Jul 31, 2011)

Xosted said:
			
		

> I know it has been a long time but this issue is still not solved.


Did you check the motherboard/system manufacturer's web site to see if a BIOS update is available?


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## Xosted (Jul 31, 2011)

I finally found a solution to my problem.

There is such thing that monitors temperatures in FreeBSD and it is the ACPI Thermal. It reads values from the BIOS which define temperature limits. In my case, these values are bogus (60 degrees on a server system...) causing FreeBSD to initiate shutdown as soon as the limit is reached.

To solve it, I added these two lines to /etc/sysctl.conf:

```
hw.acpi.thermal.user_override=1
hw.acpi.thermal.tz0._CRT=XXC
```

The first line allows to override values read from the BIOS and the second sets the desired limit (with a trailing C for celsius). After reboot, the system can go up to the new limit without shutting down.

I just tested it. Hope it will save time and money to someone else.


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