still can play, but just unable to experience the game to the fullest as new gpus are designed to work as a game computing processor rather than a game rendering processor alone. This would let the gpu act as a physics processor as well.

It's impractical to compare dx9 and dx10 cards as they're from totally different series. It is seems to be more to a whole new product range itself.

it's still new and lots of room for improvement though, the new x1950xt can't utilize the full ability of the ddr4 memory as it is bottlenecked by the gpu itself.