FX5900XT : 2dmode 300/700 , 3dmode 400/700
The gainward is the same! BUT you can safely overclock it (at least) to the numbers you see on the box. Your card is not overclocked by default, it's only tested in that speed, and it's verified at that speed.
I can't overclock my 5900XT's core... this 2d/3d stuff is not really working in the CVS nvclock... altought mem overclocking works just fine.
Sry for my bad engish