When the Canadian company introduced this chip, it insisted that its graphics processors used the better and faster DX10 design. Its cards were looking so slow because they simply werent being challenged enough under Windows XP and were being tested in the wrong manner anyway.
ATI fans rallied around this statement, waiting for real DX 10 titles and always holding out hope for faster Windows XP drivers. At the time, THG predicted the performance difference between the chip families would not change much between DirectX 9 and DirectX 10, even when native DX 10 titles appeared. At the same time, message boards all over the Internet were rife with speculation. The common thread, if you will, was that ATI surely had some untapped potential in its cards that just needed to be teased out. ATI simply needed more time after all, Nvidia had six months to tweak its graphics drivers. Given enough time, ATIs drivers would be bound to improve, giving the Radeon 2900 XT the much-anticipated performance boost.
http://www.tomshardware.co.uk/DirectX10-Geforce-Radeon,review-29666.html