A reference driver, which is a software implementation that supports every Direct3D feature. A reference driver is designed for accuracy rather than speed and as a result is slow but accurate. The rasterizer portion of the driver does make use of special CPU instructions whenever it can, but it is not intended for retail applications; use it only for feature testing, demonstration of functionality, debugging, or verifying bugs in other drivers. This driver is installed by the DirectX SDK. This driver may be referred to as a REF driver, a reference driver or a reference rasterizer.
Where can i get that driver?
I see that DX runtime has D3D11Ref.dll. What's that?