[lm-sensors] Standalone driver for W83677HG-I, NCT6775F, NCT6776F

Guenter Roeck guenter.roeck at ericsson.com
Mon Feb 7 22:27:59 CET 2011


On Mon, 2011-02-07 at 15:35 -0500, Jean Delvare wrote:
> On Mon, 7 Feb 2011 09:44:12 -0800, Guenter Roeck wrote:
> > Hi Andrew,
> > 
> > On Mon, Feb 07, 2011 at 11:50:48AM -0500, Andrew Lutomirski wrote:
> > [ ... ]
> > > >
> > > > So what you'll have to do is to set a minimum speed, and the problem will go away.
> > > 
> > > I admit I'm a bit confused as to what fan2_min does.  I have a minimum
> > > (to warn?) fan speed set in BIOS, which seems to have nothing to do
> > > with the initial value of fan2_min.  Changing fan2_min will cause
> > > fan2_alarm to become set or unset, when I decrease min below input,
> > > alarm stays set until I read it once.
> > > 
> > Interesting; it means that it works, but the BIOS seems to use another set
> > of registers to set the minimum speed.
> 
> The BIOS doesn't necessarily use limit registers. It is totally
> possible that the speed is simply checked at boot time against the
> specified limit, and the hardware monitoring chip isn't even aware of
> it.
> 
> Motherboard vendors have been under- or even misusing the hardware
> monitoring features of the chips they selected for years, and while it
> gets slowly better over time, it's still dangerous to assume that they
> always know what they are doing and that they always do the right thing.
> 
Good point. Maybe not dangerous, but it might well be a fallacy or maybe
a delusion ;).

However, adding smartfan features would really require a board using it.
So that will have to wait until someone is willing to do that.

I'll do something else, though - let users configure SmartFan IV if it
was configured at startup. That should be safe enough.

Guenter






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