The D700 and the 7970 share just the same chip(same as the 280 and the W9000), nothing more.
For the rest they don't look the same, they don't come with the same form factor, they don't consume the same power, they don't run the same drivers, they don't come with the same VRAM, they don't cost the same(well they should not, unless you buy from our friends who like to sell used 7970 for the same price of the brand new D700 with twice the memory), they don't perform the same(similar in some tasks but not the same), in 3D apps they perform much differently due to the slow single thread performance of old MP, and most important they don't share your crashes in Windows. Probably they don't even smell the same.
So is indeed a different card, different from the 7970, W9000 and 280.
Not saying better or worse, just different