Arr dirty old switchable graphics are still a pain in the ars...
first, open a terminal and become root:
check if there is a 'debug' directory in /sys/kernel/
if it's not, go and add this line to /etc/fstab
none /sys/kernel/debug debugfs defaults 0 0
You should now see a debug directory in /sys/kernel
check if the vgaswitcheroo directory exists in /sys/kernel/debug
if not, make sure to use Intel and Ati Foss drivers ( not fglrx )
once you see the file /sys/kernel/debug/vgaswitcheroo/switch you're ready to party hard!
If you want to use the intel card, just paste in a terminal (as root)
echo DIGD > /sys/kernel/debug/vgaswitcheroo/switch
now log out and in again ( not rebootin'! ) -> welcome to the intel card's power
if you want to switch to the ati card, do same as above but paste this time
echo DDIS > /sys/kernel/debug/vgaswitcheroo/switch
and you're ready to fire more 3d performance up!
if your laptop's fan is always on, this might mean that both cards are activated.
as you're only using one at a time, we simply power the unused one off:
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
you can always check wich card is currently running with this command
i want you to notice at this time, that the intel's and the foss ati driver's 3d-performances are ... well ... not actually that awesome. And the foss ati driver's powermanagement is just crap or no one ever implemented that i dunno...
if you desire full 3d performance and working powermanagement (you know, there is a difference between having 2h of batterylife or 6h ..) you can still try to fight with fglrx ( ati's propetary driver ). Once you made it working with fglrx, you can simply switch graphic cards via the ati catalyst control center ( including re-logins ). But fglrx is a tricky * ... i might be a long dark path to success - if it's ever working on one's machine ...
however, check this site for more details about switchin' with foss drivers and vgaswitcheroo: