# CPU not entering C-states [Solved]

## ericxx2005

I've already asked this on Arch's forums, but I've changed distros back to Gentoo, so I guess it belongs here:

I just bought a Gateway P-6831FX, which has a T5450 processor.  lspci shows a lot of unknown devices, so maybe that's the root of the problem, but I'll ask anyways.  Powertop shows the cpu being in C0 at all times, it there something I'm missing?

Cn                Avg residency       P-states (frequencies)

C0 (cpu running)        (100.0%)        1.67 Ghz     0.0%

C1                0.0ms ( 0.0%)         1333 Mhz     0.0%

C2                0.0ms ( 0.0%)         1000 Mhz   100.0%

C3                0.0ms ( 0.0%)

Wakeups-from-idle per second : 92.5     interval: 5.0s

Power usage (ACPI estimate): 27.2W (1.6 hours)

Top causes for wakeups:

  47.1% ( 79. :Cool:        <interrupt> : iwl4965, uhci_hcd:usb1, ohci1394, nvidia

  17.5% ( 29.6)      <kernel IPI> : Rescheduling interrupts

   6.0% ( 10.2)     mixer_applet2 : schedule_timeout (process_timeout)

   4.7% (  8.0)   <kernel module> : usb_hcd_poll_rh_status (rh_timer_func)

   3.8% (  6.4)              Xorg : do_setitimer (it_real_fn)

   3.3% (  5.6)       <interrupt> : uhci_hcd:usb3, ehci_hcd:usb7

[/url]

Original post: http://bbs.archlinux.org/viewtopic.php?id=43425

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## El_Presidente_Pufferfish

Are you using a cpu speed governor other than performance?

Try switching to ondemand, conservative, or powersave

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## ericxx2005

I'm using ondemand with cpufreq-utils.

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## ericxx2005

I don't know if this helps, but suspend/hibernate don't work either.  Is there any more information I can post to help?

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## seadog

I have this exact same C state problem using 2.6.24(-r1) using a core 2 duo, i get other C states being used in 2.6.21-r7, but not in 2.6.24

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## ericxx2005

Dmesg shows:

```
ACPI: SSDT BFED8181, 01F6 (r1  PmRef  Cpu0Ist     3000 INTL 20050624)

ACPI: SSDT BFED7C71, 048B (r1  PmRef  Cpu0Cst     3001 INTL 20050624)

ACPI: Medion 41700 detected - limiting to C1 max_cstate. Override with "processor.max_cstate=9"

ACPI: processor limited to max C-state 1

ACPI: CPU0 (power states: C1[C1] C2[C2] C3[C3])
```

Which suggests that somewhere along the line that states below C1 aren't going to work, which I don't know why.   I can't even get it to C1 though.  I tried your suggestion of downgrading the kernel to 2.6.21, but that didn't seem to change anything.

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## ericxx2005

Putting:

```
processor.max_cstate=9 max_cstate=9
```

as a kernel option in menu.lst works.

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