The NVIDIA 6600GT chip is based upon their NV4x architecture. NVIDIA introduced the 6800 Ultra, the high-end part in April of 2004 to a lot of acclaim. In a historical tradition, NV released chips based upon this architecture for the mid-range, performance and mainstream markets. These chips are the 6800, the 6600 and the 6200 series.
Key features of the NV4x family include support for Microsoft DirectX 9.0 Shader Model 3.0 (Pixel Shader 3.0 and Vertex Shader 3.0), render to texture, 32-bit floating point precision per component, 16-bit texture blending and others I've covered in my 6800 Ultra, 6800GT and 6600GT reviews that I've already published.
This currently is the most feature rich family of graphics cards available, with ATI's SM 3.0 parts not due till later on this year. Of course features are only important if game makers use them. I expect with the advent of more cards supporting this standard this year, we'll see games make use of the features. There are a couple of games available with support, including Far Cry but the vast majority of games released today support the least common denominator in features, which is DirectX 9.0 Pixel Shader Model 2.0.
