https://bugs.freedesktop.org/show_bug.cgi?id=26891

--- Comment #50 from Alex Deucher agd5f@yahoo.com --- (In reply to comment #49)

Is the BusID line in the intel device section not needed? What is needed for X to automatically detect multiple GPUs properly and show some video output from the correct card?

You'll need to use vga-switcheroo to select the card you want to use. Then you should be able to start X without any config and it will start on the one selected by vga-switcheroo. Having two device sections as your config does will force X to try and start on both devices.