LinuxQuestions.org - ACPI temperature reading makes my CPU throttle

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ACPI temperature reading makes my CPU throttle

Hi,

when on batteries my laptop CPU throttles and becomes unusable. I've been searching the forums and found the cause of the problem, but I need your help to solve it.

The problems is, independent of what CPU frequency mode I am on, at one point ACPI reaches the trip points and the CPU throttles. The problem is that sensors gives me a temperature less than 50C but the ACPI reads more than 90C.

Here is my data:
OS: Ubuntu
kernel: 2.6.24-16-generic
laptop model: HP dv5000
CPU: AMD Turion 2GHz

output of "cat /proc/acpi/thermal_zone/THRM/trip_points"

Code:

critical (S5):          94 C

passive:                90 C: tc1=2 tc2=5 tsp=50 devices=CPU0

Output of "sensors"

Code:

k8temp-pci-00c3

Adapter: PCI adapter

Core0 Temp:  +50.0°C

Output of cpufreq-info

Code:

  driver: powernow-k8

  CPUs which need to switch frequency at the same time: 0

  hardware limits: 800 MHz - 2.00 GHz

  available frequency steps: 2.00 GHz, 1.80 GHz, 1.60 GHz, 800 MHz

  available cpufreq governors: userspace, powersave, ondemand, conservative, performance

  current policy: frequency should be within 800 MHz and 2.00 GHz.

                  The governor "ondemand" may decide which speed to use

                  within this range.

  current CPU frequency is 800 MHz.

output of "cat /proc/acpi/processor/CPU0/throttling"

Code:

state count:            8

active state:            T0

state available: T0 to T7

states:

  *T0:                  100%

    T1:                  87%

    T2:                  75%

    T3:                  62%

    T4:                  50%

    T5:                  37%

    T6:                  25%

    T7:                  12%

"cat /proc/acpi/thermal_zone/THRM/temperature" always gives me 0, the only time I can get a reading is when the laptop is in battery mode and the ACPI temperature is higher than 90C. When the 90C point is reached the throttling starts from T0 and goes all the way down to T7 very quickly.

I'm not sure what else I should include in this post.

Any help with the problem would be appreciated, as I can't use my laptop in battery mode.

Regards.

Quote:

Originally Posted by uraldinho (Post 3227864)

Hi,

when on batteries my laptop CPU throttles and becomes unusable. I've been searching the forums and found the cause of the problem, but I need your help to solve it.

It seems that ACPI doesn't work fine. See on the ACPI-linux website.

I see a couple of things:

1. This may be a bug. You're using kernel 2.6.24; upgrade to 2.6.26, which may fix this bug if it really is one. You'll probably want to upgrade lm_sensors as well.

2. You're using the "ondemand" governor. Try setting the "performance" governor and see what happens.

Let me know if this works.

Mike

Thanks for your replies.

Kernel 2.6.26 gave me the same results. Also, it doesn't matter if I use the CPU in "ondemand" or "performance" mode, it always goes into throttling mode after a minute of use on batteries.

I think I found what the problem is, but I don't understand why it is happening.

The problem is that I recently replaced my battery, and this problem happens only on the new battery. All the specifications of the battery are the same as the old one. I've compared all the data in "/proc/acpi/battery/BAT1/" and they are identical.

I don't understand why one battery makes my ACPI thermal zone hit 90C instantly but the other one doesn't.

I should add that my new battery doesn't cause me the same problem in XP, this happens only in Ubuntu. "HP battery health checker" in XP tells me that my new battery is fine.

Is it possible that my new battery gives slightly higher current or voltage than the old one and that sets off one of the sensors? But then, why is the reading in "/proc/acpi/battery/BAT1/" normal?

Wow. I've never heard of anything like this! My only suggestion is to run it by the ACPI guys (I'm sure there's a list or forum for them somewhere). This is just bizarre.

Mike

Quote:

Originally Posted by storkus (Post 3229435)

Wow. I've never heard of anything like this! My only suggestion is to run it by the ACPI guys (I'm sure there's a list or forum for them somewhere). This is just bizarre.

Mike

thanks for your interest.

It's possible that there is something wrong with the battery and that interferes with the laptop. It is definitely a strange problem.

Just a quick update in case someone else has the same problem.

I said in my earlier post that the problem only occurs in Linux, but it happens in XP as well.

The problem is definitely with the battery. I don't understand why it is happening. The battery somehow makes my ACPI register high temperature in the core. The laptop doesn't feel hotter than normal, but the sensor readings go off the chart.

I'm gonna return the battery as faulty and hopefully I will have a better battery next time.

Regards