I have a 865G chip and I can tell you how I got 3D running (don't know if this helps with 855 either, but the driver is the same: i810):
1. run Yast Online Update to get the latest XFree86 updates (this should fix it already)
2. if not, it gets more complicated: follow this description:
The patch also works with other kernel versions. If you have the original SuSE kernel, you may want to try it without patch first.
Additionally you'll need to delete the link /lib/modules/<kernelversion>/build, which points to the wrong place (/usr/src/linux-<version>-obj instead of /usr/src/linux-<version>) and create it pointing to the 'real' source directory.
3. if this still doesn't work, recompile the kernel with agpgart compiled into the kernel (instead of a module, as it is in the default configuration). This should enable you to activate the 3D driver.
I have tested all three options, they all worked for me.