There are two components of interest to people with each DirectX release. There's the Software Development Kit (sdk) with debugging .dlls for programmers writing applications using DirectX . Then there's the retail run time, which are the APIs games and programs use.Source: NeoWin
DX 9.1 refers to the SDK release called "DirectX 9.0 SDK Summer Update 2003" (which ships with the DX 9.0b retail runtime)
DX 9.2 refers to the SDK released called "DirectX 9.0 SDK Summer Update 2004" (which at this time also ships with the DX 9.0b retail runtime).
A lot of hardware sites and gaming sites are getting confused over this issue because in the past a new SDK release (DX 8.0, 8.1, etc) also meant a new runtime release. This is not the case with the DirectX 9.0 SDK updates. The runtime - which is of interest to the hardware and gaming sites - is frozen on DirectX 9.0b while the debug .dlls, shader debugger, and samples in the SDK are getting updated.
I've heard both names for the SDK - DirectX 9.2 and DirectX 9.0 Summer 2004 SDK Update - used internally so I think that might be causing some of the confusion externally. I don't know if both names are official for the project.
Microsoft clears up Direct X 9.0c/9.1/9.2 naming confusion
Posted on Wednesday, Feb 04 2004 @ 20:29 CET by Thomas De Maesschalck
Microsoft does an effort to further clear up the confusion regarding the naming of the next update of DirectX: