Q6600 CPU Frequency Scaling Problem / Bug

[Hakan BAYINDIR <hakan@bayindir.org>]

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Hi,

I'm running Debian testing on an Intel Core2Quad Q6600 with 4GB DDR2 RAM
on a MSI P35 Platinum board since December 07. When I first migrated my
system on December (I've installed Debian as etch beta1 and upgrading
since), every core of the CPU was scaling their frequency independently.
After installing 2.6.22, The cores started to scale in a synchronized
way. I.e. when a core needs to speed-up, every core speeds up in sync.
The weird thing is, I have another clone of this OS at my office running
on a core 2 duo processor and that system scaled its processors
independently.

The ganged scaling behavior is also consistent with the
/sys/devices/system/cpuX/cpufreq/affected_cpus file and cpufreq-info
command. Both of them shows that all CPU's speeds are need to be in sync
while there's really no need. Also Ubuntu 8.04 Live CD exhibits the same
behavior and this behavior can be verified under sysfs again.

Is it a bug? Is it expected? I can provide more information if it's
needed. I'm attaching cpufreq-info's output as a reference.


Cheers and Regards,


-- Hakan.


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cpufrequtils 002: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to linux@brodo.de, please.
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 0 1 2 3
  hardware limits: 1.60 GHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.14 GHz, 1.87 GHz, 1.60 GHz
  available cpufreq governors: userspace, powersave, ondemand, conservative, performance
  current policy: frequency should be within 1.60 GHz and 2.40 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz.
analyzing CPU 1:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 0 1 2 3
  hardware limits: 1.60 GHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.14 GHz, 1.87 GHz, 1.60 GHz
  available cpufreq governors: userspace, powersave, ondemand, conservative, performance
  current policy: frequency should be within 1.60 GHz and 2.40 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz.
analyzing CPU 2:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 0 1 2 3
  hardware limits: 1.60 GHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.14 GHz, 1.87 GHz, 1.60 GHz
  available cpufreq governors: userspace, powersave, ondemand, conservative, performance
  current policy: frequency should be within 1.60 GHz and 2.40 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz.
analyzing CPU 3:
  driver: acpi-cpufreq
  CPUs which need to switch frequency at the same time: 0 1 2 3
  hardware limits: 1.60 GHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.14 GHz, 1.87 GHz, 1.60 GHz
  available cpufreq governors: userspace, powersave, ondemand, conservative, performance
  current policy: frequency should be within 1.60 GHz and 2.40 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz.

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