After installing Snow Leopard, the max resolution when connecting the CD 30 inch to the XServe (Early 2008) is 1280 x 800. Under Leopard, the CD worked with 2560 x 1600 as it should be.
No software updates pending, I am at 10.6.8. When disconnecting the monitor, the max resolution rises to 1680 x 1050.
The X1300 is the original Apple "Xserve Graphics Upgrade Kit" and works properly, but not under Snow Leopard.
What can I do?
Xserve (Early 2008), Mac OS X (10.6)