The Inquirer reports that Microsoft stated at the annual Siggraph conference that DirectX 10.1, the upcoming next version of Microsoft's graphics API which is part of Vista Service Pack 1, will have new features that will not be able to be used on the current high-end PC graphics cards (GeForce 8800/Radeon 2900).

Here's the thing. DX10 hardware - such as the GeForce 8800 or the Radeon 2900 - won't work with the new 10.1 features. The 0.1 revision requires completely new hardware for support, thus royally cheesing off many gamers who paid top whack for their new hardware over the last few months on the basis of future game compatibility.

But these gamers shouldn't fret too much - 10.1 adds virtually nothing that they will care about and, more to the point, adds almost nothing that developers are likely to care about. The spec revision basically makes a number of things that are optional in DX10 compulsory under the new standard - such as 32-bit floating point filtering, as opposed to the 16-bit current. 4xAA is a compulsory standard to support in 10.1, whereas graphics vendors can pick and choose their anti-aliasing support currently.

In related news, ExtremeTech has some more DirectX 10.1 Details at SIGGRAPH:

This is business as usual, as far as DirectX is concerned. DX 10.1 hardware will be backwards compatible with DirectX 10, but current DX10 hardware won't be forward compatible. So games looking to support DX 10.1 still need a DX 10 rendering path to support today's DX10 cards. Think of it like when Microsoft released DirectX 9.0c with added Shader Model 3.0 support. Also, don't worry too much about it requiring SP1 (which isn't out yet). The DX 10.1 SDK only recently was made available, and by the time supporting hardware and DX10.1 are released to end users somewhere in the first half of 2008, SP1 should be readily available.

What are the changes? DX 10.1's goals are to offer the "complete" DX 10, giving developers better control over image quality and making mandatory some of the things that are optional in DX 10. For example, 32-bit floating point filtering is optional in DX10 (16-bit FP filtering is mandatory), but will be mandatory in DX 10.1. Also, in DX 10, the number of multisample anti-aliasing samples is optional-DX 10.1 will make 4x AA mandatory, and require two specific sample patterns. Graphics cards can offer more sample patterns, and developers can query them in their shaders. Graphics cards that are DX 10.1 compliant will have to offer programmable shader output sample masks and multisample AA depth readback. Game developers will be able to index into cube maps and perform bitwise copies from uncompressed textures to block-compressed texture formats