This post is the follow up of this one. Direct3D 11 is a superset of Direct3D 9/10/10.1. Microsoft has relaxed the way Direct3D will work on the upcomming Windows 7 and if a Direct3D 9 graphics card is present, it will run. But the nice feature is that a Direct3D 9 card will be able to run Direct3D 10.x and Direct3D 11 applications! How? By software emulation. Direct3D 11 will be able to run in software mode all 3D features that are not supported by the graphics card. In the worst case, if Direct3D 11 doesn’t find any graphics adapter (there is always a graphics card in a computer but either the graphics card does not support Direct3D 9+ or the graphics drivers are not installed).
The software mode of Direct3D 11 is based on WARP: Windows Advanced Rasterization Platform. WARP is a high speed and fully conformant software rasterizer. Maybe Microsoft already targets Intel’s Larrabee…
More information about WARP: Windows Advanced Rasterization Platform (WARP) In-Depth Guide.
For french readers: Direct3D 11 Fonctionnera aussi sans Carte 3D grâce à WARP! @ Geeks3D VF