Good find but hmmm...something is wrong with this chart. They have the 7990 below the 7970 . . . and both of those below a GTX 780. I wonder what compute code they are testing exactly?
Maybe it has to do with how Direct Compute functions? With the 7990 rating, it might be a single core rating (unfair bias) as that card has a lower stock clock then then the 7970.
I'm not sure if I buy into M$ Direct Compute benchmarks. It's only one aspect of GPU performance. And I not think (correct me if I'm wrong) DX11 APIs have any bearing on real world BOINC apps.