Shader Model 6.1 is a superset of Shader Model 6.0.

The main additions are as follows:

• SV_ViewID. This feature enables instancing of the graphics pipeline by "view", in a manner that is orthogonal to draw instancing.
• SV_Barycentrics. This is a new system-generated value available in pixel shaders, used for example to perform interpolation over small or unaligned values like a few bits from a 32-bit value.