ACPI PCC Probe Failed is the error that pops up instead of the default GRUB loader after I updated my kernel to 3.19.

I searched around and couldn't find much information except that it is a known error and it is registered in kernel.org's launchpad https://bugzilla.kernel.org/show_bug.cgi?id=92551. My question is, is anyone else facing it?, what are the impacts of this? And if only an update in the future can fix it, any suggestions or safety tips till then?

  • 4
    I have this error after upgrading to Vivid Vervet. Machine displays error and hangs, will not proceed any further with boot. Pretty catastrophic, suggests that message not entirely harmless (despite conversation below)?
    – CnrL
    Apr 24, 2015 at 13:47
  • My question is, is anyone else facing it? Yes. Me too!
    – Cornelius
    Apr 24, 2015 at 14:23
  • Stuck on it too
    – yPhil
    May 3, 2015 at 10:02
  • Same problem after I upgraded to kernel 3.19.0-21
    – Tarik
    Jun 21, 2015 at 15:12
  • 1
    @Sardinha94410, you can find Ubuntu kernels at kernel.ubuntu.com. I downgraded to v3.18, kernel.ubuntu.com/~kernel-ppa/mainline/v3.18.17-vivid
    – Lordbalmon
    Jul 8, 2015 at 16:52

4 Answers 4


Apparently it is a harmless message related to a 'PCC' driver:

So it looks like you build the PCC mailbox driver which is new in 3.19-rc and that driver fails to load, because it doesn't find hardware to work with.

The message is harmless, but it also is not useful. The driver in question seems to be overly verbose to me in general.

That is what I gleaned from this conversation.

  • I see, so the GRUB disappearance is totally unrelated you think? It is possible, I forgot to run the update-grub command after updating the kernel, I will try it and get back soon.
    – Lordbalmon
    Feb 13, 2015 at 15:29
  • 1
    @Lordbalmon if you update or install the kernel using apt-get or any other ubuntu package management or update tools you shouldn't need to run update-grub, the system should run that as part of the installation unless you compiled your own kernel or something.
    – mchid
    May 13, 2015 at 6:04
  • @mchid, that is possible, though it was not a compiled kernel, I downloaded the .deb files and tried manually updating it.
    – Lordbalmon
    May 13, 2015 at 11:43
  • @Lordbalmon You do know you can manually perform updates with sudo apt-get update followed by sudo apt-get dist-upgrade correct? If you are not running vivid and want to run kernel 3.19 I understand you have to download it but otherwise, you should be using the package manager.
    – mchid
    May 13, 2015 at 12:08

ACPI PPC probe failed. is related to a new ACPI interface PCC (Platform Communication Channel), which is defined by UEFI.

You may see this in your output of journalctl:

$ sudo journalctl
Aug 16 23:10:55 x kernel: **PCCT header not found.**
Aug 16 23:10:55 x kernel: **ACPI PCC probe failed.**

These are the returns if the code does not find the ACPI interface which only some very new devices have or if it actually fails to read/write to the interface if it is present. The code was written for upstream releases. If you read the emails in the filed bugs below you will find information that supports my statements and you can read the return messages in the code itself in the GitHub link above.

http://permalink.gmane.org/gmane.linux.power-management.general/56400 http://comments.gmane.org/gmane.linux.acpi.devel/73411

I hope this helps to clarify some things.


I [Solved] the problem by changing the motherboard settings. For my motherboard (access this at boot, not through Ubuntu) I went to Advanced > System Agent > Graphics > iPGU Multi-Monitor and set it to "enable." I left all of the other system agent graphics settings on auto. After that the boot and ACPI problems (including a shutdown hang, crashes, freezes, monitor shutdown) stopped.

Every motherboard vendor has its own settings. The problem seems to be a northbridge snafu between the onboard Intel graphics and the Nvidia card. So, it may takes several visits to your motherboard setup to find the right combination of settings that works for you. This problem was new to me under 15.04, and may be due to a change in how Ubuntu handles such graphics disputes.

(My motherboard is ASUS P8Z77-V LX LGA 1155 Intel Z77)

  • similar case, ROM problem, I changed "ACPI HPNET (disabled)" to enabled... but not work... Oct 1, 2015 at 20:44

I've filed a bug for this with an upstream fix to turn this error message into a debug message, this will hopefully land in the next kernel SRU release cycle


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