Switching between graphics cards
I've just bought an Asus laptop which is equipped with two graphics cards; one integrated in the intel i3 CPU and a Radeon Mobility HD5145.
Will Ubuntu switch between the cards to balance power/performance? i.e. only use the Radeon when the demands placed on the integrated card are too great?
No, Ubuntu will not switch between the cards. This is known as a hybrid graphics system.
If you look in your /var/log/Xorg.0.log you can see which driver is loaded (page down a few screenfuls and look for RADEON(0) or intel(0).
The only way I know of to force which card to use is to specify the PCI Bus ID of the graphics card. You get the Bus ID from lspci. It's also usually shown near the top of your /var/log/Xorg.0.log. Then, set up your xorg.conf with a device section and put
BusID "PCI:0:0:1"
or whatever bus id you want. You don't need to specify the video driver as well (but it can't hurt).
David Airlie has worked on making hybrid graphics work better. His blog has some interesting info about it...
Searching for 'linux hybrid graphics' may turn up other useful examples and details about it.
Right now you can use the GUI provided by Ubuntu Control Center to switch between GPUs, but it only works with the opensource drivers.
http://code.google.com/p/ucc/
http://www.omgubuntu.co.uk/2010/08/ubuntu-control-centre-0-5-brings-gpu-switching-to-linux/
Your model has an AMD discrete graphics card, so you have two options:
- try the latest closed-source Catalyst Driver for login/logout card switching, or
- try vga_switcheroo and open-source graphics drivers with the graphical vga switching already installed. See this YouTube video.