Hi,

I've been digging throught the data sheets and there are only information about 4:3 resolutions.

Digging through the framebuffer code, I found LCD_1680x1050 (xgi-kernel-fb/xgi/vgatypes.h) which indicates that my screen's resolution might be supported, but in other sections of the code there are again only 4:3 resolutions mentioned.

Does it support widescreen resolutions (particularly 1680x1050) or does it not?

It'll support any resolution you can create a modeline for. As for generating modelines, well.. that is up to you (plenty of docs on the web for it). The fbset toolkit might help you out.