After enabling the hidden BIOS options for Native ASPM and Native PCIE Runtime PM and disabling the C-states, I got rid of the issue (a hard CMOS reset was necessary for the BIOS modification to fully kick in)
The C-states continued to work in Ubuntu, though, due to the nature of the intel_idle built-in driver. I am currently investigating which one of the above mentioned three BIOS settings triggers on the issue. Even if they aren't part of the problem, Native ASPM and PCIE PM gave me much better CPU temps (seem to require the pcie_aspm=force and pcie_aspm.policy=powersave kernel boot flags to work, otherwise neither BIOS nor the OS perform power management) Modifying a Zenbook BIOS turned out to be very simple -- you simply download the latest official BIOS, open it in an AMI APTIO BIOS modification utility, look for the hidden options you want to enable and finally change their access level from Default to User. Then you flash the modified BIOS file using either AFUDOS with /X flag or ASUS Emergency BIOS Restore (rename UX21EAS.214 to UX21E.BIN, put it on a flash stick formatted as FAT16 with a partition size <1Gb, insert it in a USB 2.0 slot and power on the ultrabook while pressing Ctrl + Fn + Home, release the said buttons after the ASUS logo appears -- the device will force-reflash its BIOS with the file from the flash stick) -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1446027 Title: SNA acceleration causes sudden shutdowns and corrupts CMOS data on the the Asus UX21E ultrabook on a wide variety of kernels since at least Ubuntu 14.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1446027/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp
