So ATI has now revised Anisotropic Filtering a bit. The x850 supports up to 16 levels of Anisotropic Filtering (AF); 2, 4, 8 or 16 texture samples. The user can select bilinear filtering or trilinear filtering by selecting either performance or quality mode in the driver properties.
"SMOOTHVISION HD anisotropic filtering supports 2, 4, 8, or 16 texture samples per pixel. Each setting can be used in a performance mode that uses bilinear samples, or a quality mode that uses trilinear samples. There is also a new capability to support intermediate modes, to help strike the ideal balance between performance and quality."