xserver-xorg-video-ati high power usage since Mint 15

[halfgaar]

Since my upgrade from Mint 15 to Mint 16 (KDE version), the battery life of my Samsung Series 7 has been significantly reduced (it wasn't great to begin with). It seems to be caused by the open source Ati driver for my Radeon HD 8730M.

With Mint 15 and the open source driver, I had about 13W of idle power use (as outlined http://forums.linuxmint.com/viewtopic.php?f=49&t=150985). I reinstalled to get Mint 16. Now my idle power use is about 17-18 Watt. In both cases, screen brightness was the same (30%). When I install fgrlx, power use is about 12-13 Watt, but 3D doesn't work (and apps that use it, crash).

The result of this is, that I only get about 2-3 hours of life out of my 57 WattHour battery (7 hours in Windows, reportedly).

Laptop details:

- Samsung Series 7 730U Ultrabook.
- Radeon HD 8730M GPU.
- Ivy Bridge Dual core Intel Core i7-3537U.
- LiteON 128GB SSD.
- Kernel: 3.11.0-12-generic x86_64
- Mem 810.8/9886.6MB
- xserver-xorg-video-ati: Version: 1:7.2.0-0ubuntu10
- xserver-xorg-video-radeon: Version: Version: 1:7.2.0-0ubuntu10
- xserver-xorg: 1:7.7+1ubuntu6

[halfgaar (wiebe-halfgaar)]

BTW, power use is a lot better when I enable kernel parameter radeon.dpm=1. Power use is about the same as Mint 15 now (about 13-14W). However, I never enabled radeon DPM on Mint 15, so I wonder why that was so much better.

The videocard is a muxless Intel integrated with the aforementioned Radeon HD 8730M, BTW.