Can T520+Bumblebee run an external monitor via DisplayPort?

Question

Using 64-bit Ubuntu 11.10 and integrated (Intel) graphics, I can run the 1600x900 laptop display plus a 1600x1200 external monitor connected to the VGA adapter. But my external monitor is 1920x1200 so I have black stripes on each side.

I believe the resolution is limited like this as the maximum resolution available from the Intel GPU is 2560x1600 = 4,096,000 pixels and I'm asking for a 3520x1200 = 4,224,000 display (with 1200x300 lost above the laptop screen). At 3200x1200 = 3,840,000 pixels, the Intel GPU seems happy.

Under Windows, the same limit exists when using the VGA adapter, but if I turn Optimus on then I can connect the external monitor to the DisplayPort and get its full resolution and an extended desktop.

I've seen that Bumblebee can run apps on the DisplayPort using the 'optirun' command. My question is: can Bumblebee run the DisplayPort in concert with the Intel card running the laptop screen creating a large virtual desktop (as on Windows)?

If so, are there any pointers to how to do this? I tried once, failed, and dropped back to Integrated Graphics (and black stripes) as I could find no reports of this configuration working.

Answer 1

I have a W520, but I think this information should hold also for the T520 (though there are some minor differences between the configurations of the two regarding the VGA port). As far as I can tell, the Display Port is connected directly to the Nvidia card. When in "Optimus" mode (set in the bios), the internal Thinkpad display is controlled by the integrated card. Since xrandr cannot handle multiple graphics cards controlling the same X session (as far as I can tell), you must use Xinerama if you want to stay in the "Optimus" bios mode (this is without bumblebee) to have a single desktop across all screens. This means creating a custom xorg.conf. Your other option is to switch to "Discrete" graphics mode in the bios so that the nvidia card is connected directly to both the Thinkpad display and the DisplayPort output. In this case you can use disper to easily connect and disconnect your external monitor on the fly (this is also without bumblebee).

I have prepared a blog post here outlining the situation for the W520. It also contains an xorg.conf to get you started if you want to pursue the Optimus option. In summary, I think that if you want a desktop across all screens, you will have to eschew Bumblebee.