I recently did a clean install of Fedora 15 64-bit on a new Lenovo Thinkpad T420s. This has an Intel i7-2620M, which is a Sandy Bridge processor with integrated graphics (HD 3100). It also has an Nvidia 4200M chip which has "Optimus" technology. This means that under Microsoft Windows 7 the Lenovo driver supports the full 1600x900 resolution of the LCD panel and can switch between the integrated and the discrete graphics. The BIOS lets you choose either Integrated Graphics only, Discrete Graphics only, or Optimus (switchable). RAM is 8 GB.
X works OK with the vesa driver, but only up to a maximum resolution of 1024x768. I have tried setting the BIOS to just integrated graphics and setting the driver in xorg.conf to Intel, but that does not work -- X says that it cannot find the frame buffer. I tried setting the BIOS to just Discrete Graphics and using the nouveau, nvidia proprietary, and bumblebee drivers, and all of them either refused to start X or produced a seriously messed-up screen and then locked up. Same with setting the BIOS to switchable.
For now I am willing to settle for the Intel driver or even the Vesa driver as long as I can get 1600x900 resolution, but setting that mode in xorg.conf did not help -- xrandr says that the only available resolutions are 1024x768, 800x600, or 640x480.
I can give more detailed info on the errors, but I was hoping someone would have some insight on what I should try. It would be great if someone has a xorg.conf and/or other settings that they know work. Then I can work from there.