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Axelman0

Member

Registered: 2010-12-02

Posts: 9

[Solved]Strange cpu/gpu behavior when switching between AC and battery

First off:
Intel Core 2 Duo T8300
Nvidia 8700M GT (proprietary drivers 319.32 atm, though the problem has persisted with other driver versions)
Kernel 3.9.9-1-ARCH

This has been a problem for me in the past, but it disappeard for a couple months so I figured an update had fixed it. That is also why I am skeptical that a faulty AC adapter is to blame. It also reappeared after a system update.

When I boot my computer while it is plugged in, my graphics card runs at highest frequencies (as it should), while my cpu is locked at 800 Mhz.
If I boot when unplugged, my graphics card is reported at lowest frequency and power source battery by nvidia-settings. My cpu then runs normally.
If I switch from AC to battery or vice versa without rebooting or logging out/back in again, neither the gpu nor cpu changes behavior.
After getting tired of trying to get the computer to work properly (sometimes after reboting a bunch it works), I discovered that I only needed to log out and back in again to affect the power supply changes.

This happens when booting from AC power, "frequency should be within 800 MHz and 800 MHz":

$ cpupower frequency-info
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 800 MHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.40 GHz, 2.00 GHz, 1.60 GHz, 1.20 GHz, 800 MHz
  available cpufreq governors: ondemand, performance
  current policy: frequency should be within 800 MHz and 800 MHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.
  boost state support:
    Supported: yes
    Active: yes

Is there a way to disable power saving in the nvidia driver or force it to operate as if it were always on AC power? This would solve my problem I think, since I could then boot unplugged, and plug the computer in to charge while it's running.

Last edited by Axelman0 (2013-08-13 05:44:08)

Axelman0

Member

Registered: 2010-12-02

Posts: 9

Re: [Solved]Strange cpu/gpu behavior when switching between AC and battery

I may have found a solution. If I allow the bios to load on battery power, then plug the computer in before slim and X have loaded, everything works properly. Either that or it's just a coincidence. I'm too afraid to turn my computer off to try again.

cookies

Member

Registered: 2013-01-17

Posts: 253

Re: [Solved]Strange cpu/gpu behavior when switching between AC and battery

https://wiki.archlinux.org/index.php/Laptop-mode-tools might be helpful.

Axelman0

Member

Registered: 2010-12-02

Posts: 9

Re: [Solved]Strange cpu/gpu behavior when switching between AC and battery

Thanks cookies, it turns out it's some sort of hardware issue. My AC adapter is fine, but the real solution ended up being that I must make sure my battery light is on before powering up the computer. This involves unplugging the power cord from the laptop, plugging it back in, and jiggling it around a little bit  till everything connects properly and the battery light lights up. Now that I've found that out I can shut down my system and unplug it without fear Now I'm not sure how to mark this as solved...