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[Bug 1506050] Re: intel cpu frequency is stuck at ~400mhz


Turns out that this was because I had a 'new' version of the intel
microcode that I must have downloaded from Intel itself in /lib/firmware
/intel-ucode when trying to diagnose a VM lockup a year or so ago.  It
updated my Haswell to 0x29, whether it's the upgrading of the microcode
or the 0x29 microcode itself causing the problem I'm not sure.

Using the 'vanilla' intel-microcode package without any modifications
seems to work fine.

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  intel cpu frequency is stuck at ~400mhz

Status in linux-lts-vivid package in Ubuntu:

Bug description:
  I upgraded an install of to the LST Enablement Stack for
  Vivid (kernel 3.19) that is running on a Xeon E5-1630 V3 (a Haswell
  Quad-Core) .  Booting with 3.19 would result in the system being very
  sluggish.  'cpupower frequency-info' would report that the CPU was
  running at around 400mhz, as would 'cat
  /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq'.  The CPUs
  would remain around 400mhz regardless of load.

  This was using the intel_pstate driver and the powersave governor.
  Switching to the performance governor had no effect.  Using the acpi-
  cpufreq driver also had no effect, the system was still sluggish even
  though the reported frequencies in /sys/devices/.

  Eventually I tracked it down to the original install having had the
  intel_microcode package installed at some point.  Once I removed this
  then the CPU frequencies scaled correctly with load.  FYI the
  particular version installed was intel-microcode/trusty-updates,now
  2.20140624-t-1ubuntu2 amd64.

  ProblemType: Bug
  DistroRelease: Ubuntu 14.04
  Package: linux-image-3.19.0-30-generic 3.19.0-30.34~14.04.1
  ProcVersionSignature: Ubuntu 3.19.0-30.34~14.04.1-generic 3.19.8-ckt6
  Uname: Linux 3.19.0-30-generic x86_64
  NonfreeKernelModules: nvidia zfs zunicode zcommon znvpair zavl
  ApportVersion: 2.14.1-0ubuntu3.15
  Architecture: amd64
  Date: Wed Oct 14 12:38:05 2015
  InstallationDate: Installed on 2014-08-05 (434 days ago)
  InstallationMedia: Lubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
  SourcePackage: linux-lts-vivid
  UpgradeStatus: No upgrade log present (probably fresh install)

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