The DX10.1 project was cancelled in the end. ATI used it more as a commercial stunt for their 3xxx and 4xxx GPU's. Ubisoft released a patch for Assasin's Creed that included the DX10.1 availability. It severely increased performance but they scrapped the patch afterwards. I don't know why but I experienced the performance boost myself. It was +10 avg. FPS and that's ALOT!
DirectX10.1 was never canceled, it was just ignored by all but ATI. And yes, it was part of Vista SP1 (link). It was mostly DirectX 10 "options" that would now become mandatory; I think some degree of mandatory AA and AF was part of it and that is why ATI cards used to lose so little performance when enabling AA/AF compared to NVidia, they were prepared for DX10.1.
------------------------------The capacity to learn is a gift; The ability to learn is a skill; The willingness to learn is a choice. - Rebec of Ginaz
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