[lm-sensors] w83627dhg and coretemp temperature mismatch?

[lm-sensors] w83627dhg and coretemp temperature mismatch?

[Florian Echtler]

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Hello everybody,

I have a Asus P5B-VM and after some fiddling and upgrading to 2.6.22, I
now have all thermal sensors (w83627dhg and coretemp) up and running.

However, I noticed that the readings from coretemp are always
significantly lower than those from the Winbond chip - an example:

w83627dhg-isa-0290
Adapter: ISA adapter
Vcore:     +1.29 V  (min =  +0.85 V, max =  +1.60 V) 
+12V:     +12.30 V  (min = +10.19 V, max = +13.46 V) 
+3.3V:     +3.23 V  (min =  +2.98 V, max =  +3.63 V) 
+5.0V:     +4.99 V  (min =  +4.51 V, max =  +5.50 V) 
Sys Temp:    +51°C  (high =   +16°C, hyst =   +90°C)  
CPU Temp:  +50.0°C  (high = +80.0°C, hyst = +75.0°C)  

coretemp-isa-0000
Adapter: ISA adapter
temp1:       +43°C  (high =   +85°C)                     

coretemp-isa-0001
Adapter: ISA adapter
temp1:       +42°C  (high =   +85°C)                     

As I have a passively-cooled CPU, I am a bit nervous about temperatures,
so I'm curious if somebody can explain the difference (and which one is
closer to reality ;-).

Thanks, Yours, Florian

PS: Please CC me, as I am not on the mailing list.

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Re: [lm-sensors] w83627dhg and coretemp temperature mismatch?

[Luca]

On 7/30/07, Florian Echtler <echtler@in.tum.de> wrote:
> As I have a passively-cooled CPU, I am a bit nervous about temperatures,
> so I'm curious if somebody can explain the difference (and which one is
> closer to reality ;-).

The w83627dhg chip reads the temperature from a sensors which is put
somewhere near (under?) the socket of the CPU. coretemp reads the two
sensors inside the CPU.

Luca

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Re: [lm-sensors] w83627dhg and coretemp temperature mismatch?

[Florian Echtler]

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> > As I have a passively-cooled CPU, I am a bit nervous about temperatures,
> > so I'm curious if somebody can explain the difference (and which one is
> > closer to reality ;-).
> The w83627dhg chip reads the temperature from a sensors which is put
> somewhere near (under?) the socket of the CPU. coretemp reads the two
> sensors inside the CPU.
Thanks - I suspected something along these lines. But why is the
external sensor then giving a higher temperature reading than the
internal sensors? Is there some sort of compensation built in, because
the mainboard manufacturer wants to stay on the safe side? (The
difference seems to be around 4-5 °C).

Yours, Florian

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Re: [lm-sensors] w83627dhg and coretemp temperature mismatch?

[Rudolf Marek]

Hi Florian
> Thanks - I suspected something along these lines. But why is the
> external sensor then giving a higher temperature reading than the
> internal sensors? Is there some sort of compensation built in, because
> the mainboard manufacturer wants to stay on the safe side? (The
> difference seems to be around 4-5 °C).
>   
I'm the author of coretemp driver. Intel wont tell the Tjmax temperature 
as described in the documentation so
the temperature might be a bit off. Because the CPU provides only a 
relative temperature to hottest possible, one can say
that:

temp1:       +42°C  (high =   +85°C) 

"85-42" C (relative to TjMax) so you are still 43C bellow dangerous level. In other words
if you get close to 85C it is bad, If the temperature reported by coretemp reaches 85C CPU will start to switch itself
on and off. The optimal point when to start massive cooling is set by intel usually 85-16 = 69C 

To sum it up. You are absolutely safe until 69C reported by coretemp. Above this temperature you need to cool the CPU bit more, so it never
reaches 85C.

Hope it is clear, I'm in office and so in hurry ;)


-- 

S přátelským pozdravem / Best regards / Mit freundlichen Grüßen

Ing. Rudolf Marek
SYSGO s.r.o.
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CZ-14800 Praha 4
Phone: +420 222138 627, +49 6136 9948 627
Fax: +420 296374890, +49 6136 9948 1 627
rudolf.marek@sysgo.com

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