After a discussion on a German a website, NVIDIA confirmed that the Geforce 600 series does not fully support DirectX 11.1 aka is 100% compatible. Well, it doesn't fully support the API. The GTX 680 supports DirectX 11.1 with hardware API eature level 11.0, including all optional features.
Now that does include a number of features useful for game developers such as ...
Reply directly from NVIDIA:
- Partial constant buffer updates
- Logic operations in the Output Merger
- 16bpp rendering
- UAV-only rendering
- Partial clears
- Large constant buffers
We did not enable four non-gaming features in Hardware in Kepler (for 11_1):
- Target-Independent Rasterization (2D rendering only)
- 16xMSAA Rasterization (2D rendering only)
- Orthogonal Line Rendering Mode
- UAV in non-pixel-shader stages
So basically, NVIDIA does support 11.1 features with 11_0 feature level through the DirectX 11.1 API.
"We do not support feature level 11_1. This is a bit confusing, due to Microsoft naming. So we do support 11.1 from a feature level for gaming related features."
The competitions AMD's Radeon HD 7000 "Southern Islands" GPU series is fully compliant with DirectX 11.1 (except the rebranded products from the 6000 family).