On HP G5 hardware and above, "no or unknown cpufreq driver is active on this CPU"

This document (7007251) is provided subject to the disclaimer at the end of this document.


SUSE Linux Enterprise Server 11
SUSE Linux Enterprise Server 11 Service Pack 1
SUSE Linux Enterprise Server 10
SUSE Linux Enterprise Server 10 Service Pack 1
SUSE Linux Enterprise Server 10 Service Pack 2
SUSE Linux Enterprise Server 10 Service Pack 3


On HP hardware it may appear that the utilities in cpufrequtils are not working as no driver is loaded.  The command cpufreq-info gives output similar to:

cpufrequtils 004: cpufreq-info (C) Dominik Brodowski 2004-2006
Report errors and bugs to http://bugs.opensuse.org, please.
analyzing CPU 0:
  no or unknown cpufreq driver is active on this CPU
analyzing CPU 1:
  no or unknown cpufreq driver is active on this CPU

and cpufreq-info -d gives no output.


In such a case,  the reason may be that the Power Regulator value in RBSU (ROM Based Setup Utility) is set to HP Dynamic.  The following HP document may be useful:

On page 3:

"HP Dynamic Control of P-states resides with the firmware. This mode allows the firmware to change the Pstate of the processor to match the server load. It is the default mode on HP ProLiant G5 and later servers."

Changing the Power Regulator BIOS setting to "OS Control", will allow a driver to be loaded.  For instance the powernow-k8 will load as the P-state driver on AMD-based ProLiant servers (such as the BL685c G7).


This Support Knowledgebase provides a valuable tool for SUSE customers and parties interested in our products and solutions to acquire information, ideas and learn from one another. Materials are provided for informational, personal or non-commercial use within your organization and are presented "AS IS" WITHOUT WARRANTY OF ANY KIND.

  • Document ID:7007251
  • Creation Date: 24-Nov-2010
  • Modified Date:12-Oct-2022
    • SUSE Linux Enterprise Server

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