According to Microsoft’s Sam Glassenberg, DirectX 10.1 will be fully compatible with all graphics cards supporting DirectX 10. He told that the current updates are very similar to those performed for DirectX 9 back in the days. All the company wants to do now is to increase the API life cycle. […] However, Sam confirmed that existing graphics cards may still not be able to use all the new features of DirectX 10.1.
New features include incremental improvements to rendering quality such as 32-bit floating-point operations (instead of 16-bit ones, used today by default) and obligatory support of 4x FSAA. Gamers who have already purchased contemporary DirectX 10 graphics cards shouldn’t be too upset, though, as DirectX 10.1 supposedly isn't shipping until Vista SP 1 does. Furthermore, Glassenberg stressed that applications designed specifically for DirectX 10.1 are very unlikely to appear anytime soon, because overall, “the updates aren’t that critical”.