Just a recipe for dual head on Xorg/Linux with the GMA 3100 included with my G31 chipset in case I forget.

1) Obtain “intel” xorg driver version 2.1.1 or later. Build/install.
2) Configure i915 kernel driver, load
3) Configure xorg with the following unusual parts: Monitor Identifiers should match these options under the video card Device block.

Code:

One monitor should have an

Code:

Finally, under screens you should use a Virtual parameter to tell the driver to allocate the appropriate buffer size.

Code:

One caveat- If your “virtual” desktop extends past 2048x2048 you can’t use DRI yet. Research indicates that this is a hardware limitation of the older chipsets only and should be overcome soon, but still the driver should be able to map “top to left” in any case, though it doesn’t yet. So if you want DRI you have to have vertically stacked monitors for now which is just not intuitive.

See also Wikipedia on GMA and Intel / Linux Docs for these chips.