From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guenter Roeck Date: Sun, 12 Oct 2014 17:20:59 +0000 Subject: Re: [lm-sensors] Fan Control on 6027R TRF running Debian Wheezy Message-Id: <543AB87B.8020508@roeck-us.net> List-Id: References: <5437E87B.8030206@truthbox.ch> In-Reply-To: <5437E87B.8030206@truthbox.ch> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lm-sensors@vger.kernel.org On 10/12/2014 10:15 AM, Phil Pokorny wrote: > On Sun, Oct 12, 2014 at 9:12 AM, Felix Schulthess wrote: > >>> You cannot control the fan speeds. They are managed by the onboard >>> controller. You can choose one of several profiles in the bios but that >>> is it. >> >> That explains a lot. Thank you for your help, I am going to do some >> further research in this direction and read up on FreeIPMI. >> >> Still, if I can't control the fan speeds but they are instead controlled >> by some onboard controller, then how could the installation on the >> fancontrol and lm-sensors mess up the control loop so bad? This still >> keeps me wondering. >> > > You can't control the fan speeds because there is already another device on > the motherboard that is tasked with the job of controlling them. As you > found, you can poke the control chips, but that doesn't mean you can > control the speeds predictably. Imagine two cooks in a kitchen trying to > cook different meals with the same ingredients. They come and go in the > kitchen unaware of the others meddling and confused why things are changing > when they are away. You end up with no food. Only one cook in the kitchen. > > It's also possible that when you ran SDT it's default config was to change > the BIOS/BMC setting on the fans speeds to full speed. As you found it was > a permanent change to the setting, not some strange interaction between > lm_sensors and sdt and the BMC. > > >> Maybe, the sensors somehow blocked the CPU temperature readout. This >> could have caused the superdoctor program to resort to some failsafe >> behavior (i.e. spinning the fans up to max RPM). Just wondering. > > > Also possible. > No idea how that could happen, unless there is a means for an application or kernel module to block access to specific CPU registers. That would be news to me, though. Guenter _______________________________________________ lm-sensors mailing list lm-sensors@lm-sensors.org http://lists.lm-sensors.org/mailman/listinfo/lm-sensors