Screen size on iMac 21.5, 3.06 GHz

Hi all,
I tried openSuse 11.2 on my brandnew iMac today.
Unfortunately the screen size openSuse recognizes is only 1440x1050.

My iMac screen data is:
ATI Radeon HD 4670
VRAM (gesamt): 256 MB
ROM-Version: 113-B8030C-253
EFI-Driverversion: 01.00.367
Resolution: 1920 x 1080

I have also installed Ubuntu which automatically configured everything correctly.

What can I do? Any clues?

Greetings, Ronald

Install the ATi drivers: ATI - openSUSE