Gentoo Archives: gentoo-user

From: Paul Hartman <paul.hartman+gentoo@×××××.com>
To: gentoo-user@l.g.o
Subject: Re: [gentoo-user] lm_sensors show 2 different temp. for my CPU
Date: Wed, 04 Aug 2010 14:49:05
Message-Id: AANLkTimcrOVUg=enfrc4icVnrZHE3wAoxmRZDjrFqDdQ@mail.gmail.com
In Reply to: [gentoo-user] lm_sensors show 2 different temp. for my CPU by Xi Shen
1 On Wed, Aug 4, 2010 at 6:14 AM, Xi Shen <davidshen84@××××××××××.com> wrote:
2 > hi,
3 >
4 > after i setup lm_sensors on my gentoo amd64, i ran sensors, and got
5 > the below output
6 >
7 > coretemp-isa-0000
8 > Adapter: ISA adapter
9 > Core 0:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
10 >
11 > coretemp-isa-0001
12 > Adapter: ISA adapter
13 > Core 1:      +61.0 C  (high = +74.0 C, crit = +100.0 C)
14 >
15 > atk0110-acpi-0
16 > Adapter: ACPI interface
17 > Vcore Voltage:     +1.14 V  (min =  +1.45 V, max =  +1.75 V)
18 >  +3.3 Voltage:     +3.23 V  (min =  +3.00 V, max =  +3.60 V)
19 >  +5.0 Voltage:     +4.84 V  (min =  +4.50 V, max =  +5.50 V)
20 > +12.0 Voltage:    +11.90 V  (min = +11.20 V, max = +13.20 V)
21 > CPU FAN Speed:    2556 RPM  (min =    0 RPM)
22 > CHASSIS FAN Speed:   0 RPM  (min =    0 RPM)
23 > POWER FAN Speed:     0 RPM  (min =    0 RPM)
24 > CPU Temperature:   +49.0 C  (high = +90.0 C, crit = +125.0 C)
25 > MB Temperature:    +41.0 C  (high = +30.0 C, crit = +90.0 C)
26 >
27 >
28 > at the top are my CPU temp. of the 2 cores, usually they should be the
29 > same. but at the bottom, there's another value, which is 49 in this
30 > instance. which one is the correct value? why they are different?
31
32 AFAIK, neither is wrong or correct, they are usually measuring different things.
33
34 coretemp is typically a relative temperature based on some scale like
35 0-100, using the digital thermal sensor in the CPU. It's not
36 necessarily actual temperature measurement but it's an approximation
37 that should be near a real temperature on most CPU models. In the past
38 the approximation formula has changed between kernel versions and
39 suddenly people see a 15 degrees change in coretemp, but all that
40 really changed is how it is calculated. So keep that in mind if you
41 notice a large change in coretemp someday in the future after
42 installing a new kernel but the motherboard CPU temp doesn't change.
43
44 The CPU temperature in the bottom section is from your motherboard's
45 sensors, which could be temperature very near the CPU if not inside
46 the CPU itself like coretemp.
47
48 Both values independently are useful for seeing any sudden change, but
49 there's no real value in comparing them to each other. If you want
50 actual temperature like a thermometer then the motherboard reading
51 (lower number) is probably more accurate I would guess.
52
53 Hope I didn't confuse you even more :)