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haertig 07-10-2017 06:29 PM

Question on lm-sensors output
At some time in the past, I installed lm-sensors and forgot about it.

I checked today, and I was getting output like this:


$ sensors
Adapter: PCI adapter
temp1:        +22.0C  (high = +70.0C)

Not much information there, so I ran sensors-detect to find out what I was missing. I let it run the checks that seemed harmless, but denied the ones that said they might cause problems. In the end, sensors-detect recommended I add the it87 module. So I ran "modprobe it87". Now, lm-sensors reports the following:


$ sensors
Adapter: PCI adapter
temp1:        +22.0C  (high = +70.0C)

Adapter: ISA adapter
in0:          +1.15 V  (min =  +0.00 V, max =  +4.08 V)
in1:          +1.95 V  (min =  +0.00 V, max =  +4.08 V)
in2:          +3.25 V  (min =  +0.00 V, max =  +4.08 V)
+5V:          +2.93 V  (min =  +0.00 V, max =  +4.08 V)
in4:          +3.09 V  (min =  +0.00 V, max =  +4.08 V)
in5:          +0.00 V  (min =  +0.00 V, max =  +4.08 V)
in6:          +2.05 V  (min =  +0.00 V, max =  +4.08 V)
in7:          +3.25 V  (min =  +0.00 V, max =  +4.08 V)
Vbat:        +3.30 V 
fan1:        2576 RPM  (min =  10 RPM)
fan2:          0 RPM  (min =    0 RPM)
fan3:        1285 RPM  (min =    0 RPM)
fan5:        1261 RPM  (min =    0 RPM)
temp1:        +38.0C  (low  = +127.0C, high = +127.0C)  sensor = thermistor
temp2:        +92.0C  (low  = +127.0C, high = +127.0C)  sensor = thermistor
temp3:        +37.0C  (low  = +127.0C, high = +70.0C)  sensor = thermistor
cpu0_vid:    +1.250 V
intrusion0:  ALARM

A lot more information. But the three temps at the bottom are high. Especially that +92.0C (198F) one! And the +38.0C (100F) ones are higher than I'd expect too.

This system has always run cool as a cucumber. I opened the case and tried to detect heat anywhere. It feels like it's air conditioned in there. No sign of heat at all (nothing on the Mobo, nothing near the hard drives). I could put my finger right on the CPU cooler fins and I was not able to detect anything above ambient temperature, which is 70F in my room right now. If the CPU and/or hard drives were 198F, or even 100F, I would have felt at least some temperature rise above ambient.

So is lm-sensors lying to me? It would appear so. This computer has an older Mobo and CPU:


# sensors-detect revision 6284 (2015-05-31 14:00:33 +0200)
# System: Gigabyte Technology Co., Ltd. GA-MA78G-DS3H
# Kernel: 4.4.0-21-generic x86_64
# Processor: AMD Phenom(tm) II X6 1045T Processor (six cores, 2.7GHz, 95 watt)

I am not so much worried about the above system, because shortly I will be giving it to my parents, to replace their way-too-slow old computer. I will be replacing it with the set up below (most likely - I might go Intel, but you can't beat the pricing for the older AMD CPUs/Mobo's):


AMD FX 8350 Processor with Wraith Cooler (eight cores, 4.0GHz, 125 watt)

Still an old setup, but cheap, and fine for what I need it to do. But my concern is that the FX-8350 CPU is known to run hot, so I want to learn the correct setup and use of lm-sensors.

frankbell 07-10-2017 07:41 PM

I agree that this


temp2: +92.0C (low = +127.0C, high = +127.0C)
looks off, especially as it is so out-of-range with the others.

I assume that, when you opened the box, you checked for dust build-up on the vents. If the CPU is covered (I had a computer that had a plastic cover over the CPU intended, I suppose, to channel cooling air over it), pull the cover and check for dust build-up on the cooling vanes. When I did that, I found the CPU was caked with a layer of dust. It looked like it was wearing a sweater! Even at that point, it didn't hit temperatures of almost boiling.

Another possibility is that the physical temperature sensor itself is malfunctioning is bust and not registering an accurate reading.

haertig 07-10-2017 08:11 PM


Originally Posted by frankbell (Post 5733368)
I assume that, when you opened the box, you checked for dust build-up on the vents.

I did. There was minor dust build-up, but not enough for me to want to shut it down and take the thing outside for a blast with Dust-Off. Plus, the heatsink vanes on the CPU cooler were cool to the touch. If anything was heating up, I wouldn't expect those vanes to be cool.

frankbell 07-10-2017 08:17 PM

I'd say the odds point to a faulty sensor.

One of the things I've learned is that stuff sometimes breaks.

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