Salut,
Incorrect. Ambient Occlusion runs on any DirectX 9.0c card. It is *NOT* a new feature, it is just a pixel shader. The effect has been possible since the geforce 6xxx / radeon x1xxx days (if not since the 9700 Pro). DX10.1 adds Global Illumination, which accomplishes a similar affect as AO but is superior (more realistic).
Again, AO is not a part of any spec, it is not a feature of the card or driver, it is a pixel shader. It will work on ANY card that can run pixel shader version 3.0 (might work on 2.0 as well). AO is the result of clever programming on the part of game developers, nothing more nothing less
Sourceça fait donc parti des pixel shader, ce n'est pas une option particulière.