[gentoo-user] lm_sensors show 2 different temp. for my CPU

[gentoo-user] lm_sensors show 2 different temp. for my CPU

[Xi Shen]

hi,

after i setup lm_sensors on my gentoo amd64, i ran sensors, and got
the below output

coretemp-isa-0000
Adapter: ISA adapter
Core 0:      +61.0 C  (high = +74.0 C, crit = +100.0 C)

coretemp-isa-0001
Adapter: ISA adapter
Core 1:      +61.0 C  (high = +74.0 C, crit = +100.0 C)

atk0110-acpi-0
Adapter: ACPI interface
Vcore Voltage:     +1.14 V  (min =  +1.45 V, max =  +1.75 V)
 +3.3 Voltage:     +3.23 V  (min =  +3.00 V, max =  +3.60 V)
 +5.0 Voltage:     +4.84 V  (min =  +4.50 V, max =  +5.50 V)
+12.0 Voltage:    +11.90 V  (min = +11.20 V, max = +13.20 V)
CPU FAN Speed:    2556 RPM  (min =    0 RPM)
CHASSIS FAN Speed:   0 RPM  (min =    0 RPM)
POWER FAN Speed:     0 RPM  (min =    0 RPM)
CPU Temperature:   +49.0 C  (high = +90.0 C, crit = +125.0 C)
MB Temperature:    +41.0 C  (high = +30.0 C, crit = +90.0 C)


at the top are my CPU temp. of the 2 cores, usually they should be the
same. but at the bottom, there's another value, which is 49 in this
instance. which one is the correct value? why they are different?


-- 
Best Regards,
Xi Shen (David)

http://twitter.com/davidshen84/

Re: [gentoo-user] lm_sensors show 2 different temp. for my CPU

[Paul Hartman]

On Wed, Aug 4, 2010 at 6:14 AM, Xi Shen <davidshen84@googlemail.com> wrote:
> hi,
>
> after i setup lm_sensors on my gentoo amd64, i ran sensors, and got
> the below output
>
> coretemp-isa-0000
> Adapter: ISA adapter
> Core 0:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
>
> coretemp-isa-0001
> Adapter: ISA adapter
> Core 1:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
>
> atk0110-acpi-0
> Adapter: ACPI interface
> Vcore Voltage:     +1.14 V  (min =  +1.45 V, max =  +1.75 V)
>  +3.3 Voltage:     +3.23 V  (min =  +3.00 V, max =  +3.60 V)
>  +5.0 Voltage:     +4.84 V  (min =  +4.50 V, max =  +5.50 V)
> +12.0 Voltage:    +11.90 V  (min = +11.20 V, max = +13.20 V)
> CPU FAN Speed:    2556 RPM  (min =    0 RPM)
> CHASSIS FAN Speed:   0 RPM  (min =    0 RPM)
> POWER FAN Speed:     0 RPM  (min =    0 RPM)
> CPU Temperature:   +49.0 C  (high = +90.0 C, crit = +125.0 C)
> MB Temperature:    +41.0 C  (high = +30.0 C, crit = +90.0 C)
>
>
> at the top are my CPU temp. of the 2 cores, usually they should be the
> same. but at the bottom, there's another value, which is 49 in this
> instance. which one is the correct value? why they are different?

AFAIK, neither is wrong or correct, they are usually measuring different things.

coretemp is typically a relative temperature based on some scale like
0-100, using the digital thermal sensor in the CPU. It's not
necessarily actual temperature measurement but it's an approximation
that should be near a real temperature on most CPU models. In the past
the approximation formula has changed between kernel versions and
suddenly people see a 15 degrees change in coretemp, but all that
really changed is how it is calculated. So keep that in mind if you
notice a large change in coretemp someday in the future after
installing a new kernel but the motherboard CPU temp doesn't change.

The CPU temperature in the bottom section is from your motherboard's
sensors, which could be temperature very near the CPU if not inside
the CPU itself like coretemp.

Both values independently are useful for seeing any sudden change, but
there's no real value in comparing them to each other. If you want
actual temperature like a thermometer then the motherboard reading
(lower number) is probably more accurate I would guess.

Hope I didn't confuse you even more :)

[gentoo-user] Re: lm_sensors show 2 different temp. for my CPU

[Nikos Chantziaras]

On 08/04/2010 02:14 PM, Xi Shen wrote:
> hi,
>
> after i setup lm_sensors on my gentoo amd64, i ran sensors, and got
> the below output
>
> coretemp-isa-0000
> Adapter: ISA adapter
> Core 0:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
>
> coretemp-isa-0001
> Adapter: ISA adapter
> Core 1:      +61.0 C  (high = +74.0 C, crit = +100.0 C)

This is the sensor inside the CPU.  The kernel doesn't know how to 
interpret this value on non-mobile CPUs, and it's usually off by 10C to 
15C on desktop CPUs.


> CPU Temperature:   +49.0 C  (high = +90.0 C, crit = +125.0 C)

This is the sensor on your motherboard that resides directly under the 
CPU.  This an accurate temp and the kernel knows exactly how to 
interpret the values.

Re: [gentoo-user] Re: lm_sensors show 2 different temp. for my CPU

[Bill Kenworthy]

On Wed, 2010-08-04 at 18:22 +0300, Nikos Chantziaras wrote:
> On 08/04/2010 02:14 PM, Xi Shen wrote:
> > hi,
> >
> > after i setup lm_sensors on my gentoo amd64, i ran sensors, and got
> > the below output
> >
> > coretemp-isa-0000
> > Adapter: ISA adapter
> > Core 0:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
> >
> > coretemp-isa-0001
> > Adapter: ISA adapter
> > Core 1:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
> 
> This is the sensor inside the CPU.  The kernel doesn't know how to 
> interpret this value on non-mobile CPUs, and it's usually off by 10C to 
> 15C on desktop CPUs.
> 
> 
> > CPU Temperature:   +49.0 C  (high = +90.0 C, crit = +125.0 C)
> 
> This is the sensor on your motherboard that resides directly under the 
> CPU.  This an accurate temp and the kernel knows exactly how to 
> interpret the values.
> 
> 


This is windows specific but has lots on how Intel/AMD work.
http://www.alcpu.com/CoreTemp/

This page seems to imply that Linux's use of coretemp is not as
"detailed" as available to windoze users and if an unknown cpu will use
a default value which may be incorrect.
http://www.mjmwired.net/kernel/Documentation/hwmon/coretemp

The lm_sensor temperatures (and voltages) are always highly suspect,
usually being based on users experiments rather than manufacturer
information which is usually not available.  Also, I suspect variation
even between motherboards of the same type as sometimes the supposed
lm_sensors values for one of my systems (often cpu voltage) are not even
close.

BillK

Re: [gentoo-user] Re: lm_sensors show 2 different temp. for my CPU

[Xi Shen]

thanks to both of you. :)


On Wed, Aug 4, 2010 at 11:22 PM, Nikos Chantziaras <realnc@arcor.de> wrote:
> On 08/04/2010 02:14 PM, Xi Shen wrote:
>>
>> hi,
>>
>> after i setup lm_sensors on my gentoo amd64, i ran sensors, and got
>> the below output
>>
>> coretemp-isa-0000
>> Adapter: ISA adapter
>> Core 0:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
>>
>> coretemp-isa-0001
>> Adapter: ISA adapter
>> Core 1:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
>
> This is the sensor inside the CPU.  The kernel doesn't know how to interpret
> this value on non-mobile CPUs, and it's usually off by 10C to 15C on desktop
> CPUs.
>
>
>> CPU Temperature:   +49.0 C  (high = +90.0 C, crit = +125.0 C)
>
> This is the sensor on your motherboard that resides directly under the CPU.
>  This an accurate temp and the kernel knows exactly how to interpret the
> values.
>
>
>



-- 
Best Regards,
Xi Shen (David)

http://twitter.com/davidshen84/