Ubuntu causing a "CPU Fan Failed" problem on restart

Craig Hagerman craighagerman at gmail.com
Fri Jan 12 13:20:23 UTC 2007

On 1/12/07, Gilles Gravier <Gilles at gravier.org> wrote:
> Tell us the result!

I had to get to bed (I'm in Japan - probably different time zone from
all of you), and then had a busy day of work today. Just got around to
trying things. I tried to add "acpi=off" at the end of the kernel line
in /boot/grub/menu.lst but that only resulted in a kernel panic on
reboot. Not sure why. From what I have read online I adjusted the
settings correctly.

On 1/12/07, Björn Ottervik < bjorn.ottervik at gmail.com> wrote:
>  Ubuntu is most lekly not doing anything, besides breaking the fan
> throttling. Its the motherboard thats complaining that things arent
> turning as they are supposed to be.

Agreed it IS a motherboard concern, however this ONLY happens when
restarting Ubuntu and not another OS (windows or another linux).
Therefore Ubuntu is definitely involved somehow.

I did a bit more research and found some windows message boards
describing a similar problem with people using fan & CPU scaling and
often aftermarket CPU fans (ie situations where the fan might be
spinning very slowly). In those cases it was thought that the POST (or
is that BIOS) fan sensor doesn't recognise such a slow speed and thus
throws up the error.

This sounds like my problem. As I reported the fan IS spinning on
restart when I get the message "CPU fan failed". Also, I use
lm_sensors to throttle the CPU and adjust the fan speed. (I have used
this on other installations with no issues, however.)

It occured to me that most of the time the CPU IS slowed down and the
fan is usually off. I wondered if it would make a difference if I
tried to restart with the fan at normal full speed and the CPU working
hard. I did a little experiment and ran a few games (Sauerbraten,
Enemy Territory & Nexuiz) for a while to push the machine. I checked
after and the CPU was at 55 degrees and the fan spinning at 3500 rpm.
When I then did a restart I got no error message about the CPU fan
failing. I waited a few minutes until the CPU was cool and the fan off
again and restarted - and the error message game back. So I guess I am
closer to narrowing down the problem. But just killing the sensors and
fan control utilities doesn't seem to do anything (ie it doesn't stop
the fan scaling).

I'll try playing around with more settings in the next few days and
see what more I can discover about this.


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