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Bug 171533 - Frequency in /proc/cpuinfo and /sys/.../cpuinfo_cur_freq differ
Frequency in /proc/cpuinfo and /sys/.../cpuinfo_cur_freq differ
Product: Red Hat Enterprise Linux 4
Classification: Red Hat
Component: kernel (Show other bugs)
i686 Linux
medium Severity medium
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Assigned To: Kernel Maintainer List
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2005-10-22 09:55 EDT by Dirk Gfroerer
Modified: 2007-11-30 17:07 EST (History)
1 user (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2005-11-01 11:59:07 EST
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Regression: ---
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Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
Output of /proc/cpuinfo (1.02 KB, text/plain)
2005-10-22 09:58 EDT, Dirk Gfroerer
no flags Details

  None (edit)
Description Dirk Gfroerer 2005-10-22 09:55:39 EDT
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20050921 Red Hat/1.0.7-1.4.1 Firefox/1.0.7

Description of problem:
I've got a Pentium D 830 in a Dell Dimension 9100. According to Intels hardware specification Speed Step is available for this processor. cpuspeed is running and is telling me it can switch frequencies between 2.8 GHz and 3.0 GHz. When I query /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq it is telling me most of the time the CPU(s) are running at 2.8 GHz. Exactly what I expect. However /proc/cpuinfo always shows the CPUs running at 3.0 GHz. If I take a look at my Notebook, the frequencies in /proc/cpuinfo and /sys/devices/.../cpuinfo_cur_freq change in sync.
Even when I send a SIGUSR2 to cpuspeed the frequency in /proc/cpuinfo does not change.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. cat /proc/cpuinfo
2. cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq


Actual Results:  Frequencies differ.

Expected Results:  Frequencies are identical

Additional info:
Comment 1 Dirk Gfroerer 2005-10-22 09:58:03 EDT
Created attachment 120281 [details]
Output of /proc/cpuinfo
Comment 2 Joern Gaertner 2005-10-26 06:18:25 EDT
The P4D can't do speedstep, but the frequency can be changed by the BIOS.  The
frequency in /sys is the current frequency of the CPU, and the one is
/proc/cpuinfo is the canonical frequency.

Therefore, the behavior that you are seeing is expected and gives no cause for

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