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On my VIA EPIA motherboard (using VIA VT8231 ISA bridge), I get strange output for the lm-sensors temperature reading. It always returns 32 degrees (celsius).

I have previously had correct output for temperature (my munin graphs show temperatures typically in the range of 50 to 60 degrees.

I've tried uninstalling (and purging) the lm-sensors package, have re-run sensors-detect a number of times and rebooted but nothing seems to change the output.

I am running Ubuntu Karmic Koala (9.10). Anyone got any bright ideas on what I might have missed?

uname -a:

Linux george 2.6.31-16-386 #53-Ubuntu SMP Tue Dec 8 06:39:34 UTC 2009 i686 GNU/Linux

cpuinfo:

processor       : 0
vendor_id       : CentaurHauls
cpu family      : 6
model           : 7
model name      : VIA Samuel 2
stepping        : 3
cpu MHz         : 399.000
cache size      : 64 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu de tsc msr cx8 mtrr pge mmx 3dnow up
bogomips        : 800.04
clflush size    : 32
power management:

lspci:

00:00.0 Host bridge: VIA Technologies, Inc. VT8601 [Apollo ProMedia] (rev 05)
00:01.0 PCI bridge: VIA Technologies, Inc. VT8601 [Apollo ProMedia AGP]
00:11.0 ISA bridge: VIA Technologies, Inc. VT8231 [PCI-to-ISA Bridge] (rev 10)
00:11.1 IDE interface: VIA Technologies, Inc. VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 06)
00:11.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 1e)
00:11.3 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 1e)
00:11.4 Bridge: VIA Technologies, Inc. VT8235 ACPI (rev 10)
00:11.5 Multimedia audio controller: VIA Technologies, Inc. VT82C686 AC97 Audio Controller (rev 40)
00:12.0 Ethernet controller: VIA Technologies, Inc. VT6102 [Rhine-II] (rev 51)
01:00.0 VGA compatible controller: Trident Microsystems CyberBlade/i1 (rev 6a)

sensors:

acpitz-virtual-0
Adapter: Virtual device
temp1:       +32.0°C  (crit = +60.0°C)
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3 Answers 3

Have you upgraded your kernel lately? Unless you've been tinkering with system hardware to improve cooling, your change probably came as a result of a kernel upgrade. Either the new kernel's drivers don't quite work with your particular chipset, or they enumerate the sensors differently and the sensor you're watching isn't the one you were watching before.

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Where is the sensor for the temperature?

It may not be connected or not in contact with the processor/heatsink.

If it's not in contact, it may be measuring the room temperature, and 32C sounds fairly typical for a Melbourne summer day. Do you measure the temperature several times a day?

Is it a rock-solid constant 32C at all hours of the day and night?

BTW, many readers of this page will look at your question title, and assume it's Fahrenheit (which would be a very interesting temperature, indeed)

EDIT as a result of the comment:

So, if it's on the motherboard, it's not actually measuring processor temperature. This could be better described as a 'system temperature', although you didn't describe it as anything else. Maybe a 400MHz processor didn't rate much temperature monitoring, and the sensors: temp1 critical value is only 60C. The word 'virtual' in the sensors: output is curious, though.

It doesn't seem like anything to worry about, but the question is why was it 50C before, and 32C now?

Did anything change to give better cooling of your system?

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I believe the sensor is part of the motherboard. Previously when I've been monitoring the temperature it's idled at around 50 degrees. It's a rock solid constant 32 degrees all the time the machine is on. I am graphing the data with munin and it's a flat horizontal line with no variation. –  mopoke Jan 11 '10 at 4:28

OK this is just a guess.

Are you sure the data it's reporting is in C? Sure, the printf says C at the end, but maybe it's printing F data with a C at the end without knowing it's not C.

If indeed it might be 32 F then there's an easy answer; you're getting a 0C reading from the sensor and it's being translated to F for whatever reason.

If you got a "0C" reading consistently, you might surmise you're not seeing any data from the sensor at all; I think maybe this is the case.

Hope this helps!
-pbr

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