[lm-sensors] it8705: nonsense temperature readings

[lm-sensors] it8705: nonsense temperature readings

[Hector Lahoz Grañena]

Hello
I've been interested for some time in power management and ACPI.
Well, I've come to the conclusion that the first step to achieve power management
and (most important) a silent computer is good temperature readings. So I had a look
and I found that the reading was completely meaningless. The CPU temperature showed
20 degrees Celsius 1 min. after power-on, when the room temperature was 25.
I got the datasheet of the it8705 (not a real specification, but is all I have) and
found 3 registers called "thermal diode zero degree adjustment". I also found that
the driver (version 2.6.24.2) does not use them. I've been playing around with theese
registers but I don't know which is the correct value to store there. I suppose it
depends on the diode used. The motherboard is a Biostar P4VTB.
I wonder iwhether the chip could be connected to tne internal diode of the
Pentium 4 or is it an external one on the motherboard. Really, the manufacturers
don't give much information. I wouldn't need it if they did things the right way.

i don't mean to achieve a lab accurate reading, but currently it is useless.
If you could help me in some extent I would really appreciate it.


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Re: [lm-sensors] it8705: nonsense temperature readings

[Agile Aspect]

Incidentally, if you have rack mounted computers in a computer room
with centralized air conditioning, then it's highly likely you have cold
and hot spots in the computer room.

Hence, the assumption that thermostat temperature should be equal
to the computer temperature may not be valid.

Hector Lahoz Grañena wrote:
> Hello
> I've been interested for some time in power management and ACPI.
> Well, I've come to the conclusion that the first step to achieve power management
> and (most important) a silent computer is good temperature readings. So I had a look
> and I found that the reading was completely meaningless. The CPU temperature showed
> 20 degrees Celsius 1 min. after power-on, when the room temperature was 25.
> I got the datasheet of the it8705 (not a real specification, but is all I have) and
> found 3 registers called "thermal diode zero degree adjustment". I also found that
> the driver (version 2.6.24.2) does not use them. I've been playing around with theese
> registers but I don't know which is the correct value to store there. I suppose it
> depends on the diode used. The motherboard is a Biostar P4VTB.
> I wonder iwhether the chip could be connected to tne internal diode of the
> Pentium 4 or is it an external one on the motherboard. Really, the manufacturers
> don't give much information. I wouldn't need it if they did things the right way.
>
> i don't mean to achieve a lab accurate reading, but currently it is useless.
> If you could help me in some extent I would really appreciate it.
>
>
> __________________________________________________
> Correo Yahoo!
> Espacio para todos tus mensajes, antivirus y antispam ¡gratis! 
> Regístrate ya - http://correo.yahoo.es 
>
> _______________________________________________
> lm-sensors mailing list
> lm-sensors@lm-sensors.org
> http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
>
>   


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Re: [lm-sensors] it8705: nonsense temperature readings

[Hector Lahoz Grañena]

-----  Original message ----
De: Agile Aspect <agile.aspect@gmail.com>
Para: Hector Lahoz Grañena <hectorlahoz@yahoo.es>
CC: lm-sensors@lm-sensors.org
Enviado: domingo, 24 de agosto, 2008 2:42:57
Asunto: Re: [lm-sensors] it8705: nonsense temperature readings

Incidentally, if you have rack mounted computers in a computer room
with centralized air conditioning, then it's highly likely you have cold
and hot spots in the computer room.

Hence, the assumption that thermostat temperature should be equal
to the computer temperature may not be valid.

----- End of original message ----


I think that's not the problem. The room has no air conditioning and the
air temperature measure was taken 1 m. away from the processor at
the same height. I also attached a thermocouple to the heatsink and
the readings were always higher than those from the it8705, which is
quite incoherent.


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