I was not happy with the power consumption of CentOS 6 x86_64 on a new Lenovo Thinkpad x220 Tablet and I worked on reducing it. I just wanted to share with the list one of the changes which gave me the most significant improvement.
As per http://www.williambrownstreet.net/blog/?p87, add the following kernel arguments to the GRUB boot configuration:
pcie_aspm=force i915.i915_enable_rc6=1 i915.lvds_downclock=1 i915.i915_enable_fbc=1
(in /boot/efi/EFI/redhat/grub.conf since I use EFI, /boot/grub/grub.conf otherwise)
As measured using PowerTop, this made the power consumption decrease from 20W to 11W ! (I had already decreased it from 25W to 20W with the usual tips of disabling hardware, shutting down services, switching tuned profiles, etc.)
All in all, battery time was more than multiplied by two, and the computer is now much more silent since the fan is not always running like mad in order to cool the processor. The bottom of the laptop is not anymore hot as hell.
I don’t know whether this would have an impact on other hardware, but it may be worth looking at it (even on servers?), since the above link points to descriptions of a regression in the kernel which seems more general.
As a side note, the Power Management Guide of Red Hat is a good resource (analysis tools + tuned profiles): http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html-single/Power_Management_Guide/
PS: Do you think I should book a bug in the upstream bug tracker?