The topic isn’t something new – to equip a computer with two graphic cards to make it save power. The idea bases on the fact that you don’t need high end graphical performance for your daily work and so a less powerful card is implemented aside of a big one to let the system decide on your needs. But that’s pure theory.
You might say that the concept isn’t bad at all, but let me explain: In our case, the power user card is an ATI Radeon HD card which causes many troubles with a recent kernel due to the binary drivers. As long as this card isn’t initialized, it will run on 100 percent power, converting energy to heat.
So what now? I tried to emerge the ATI binary drivers for the current kernel which worked more or less painful to get the kernel module handling the card.
Good news: It loads and the ATI Card gets initialized and gets to a sleep state. So I fired up Xorg to see if my Intel card is still active and working. But that’s where the mess really starts: Direct Rendering fails as the DRI stuff gets directed to the ATI kernel module somehow – which even crashes my graphical interface.
After some minutes I started to remember the fglrx module which is still left in the kernel memory as it’s loaded. After unloading it and restarting X, the graphical problems disappeared. So my temporarily workaround is unloading the fglrx module before I start Xorg using the intel card which saves me some troubles and heat.