1. To force Active-State Power Management to be enabled, you must edit the GRUB2 config file so open a terminal and copy/paste this:
gksu gedit /etc/default/grub
2. Then, locate the line that looks like this:
(it's on line 11 on my computer) and to the end of the line, before the last quote, addpcie_aspm=force (and a space before it), which should make it look like this:GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pcie_aspm=force"
Now double check you've edited the file correctly! Modifying this file incorrectly may cause your computer to stop booting!
3. And finally, update GRUB using the command below:
And restart your computer.
If something goes wrong, reverting the changes is pretty easy: simply open "/etc/default/grub" as root and remove "pcie_aspm=force" from the end of the "GRUB_CMDLINE_LINUX_DEFAULT" line, then run "sudo update-grub