As for memory, the 600MHz (1,200MHz effective) GDDR3 RAM is employed with a 256-bit wide bus interface between it and the core. This produces a maximum theoretical memory bandwidth of 38.4GB/s, up from 35.2GB/s for a 6800 Ultra.
But it isn’t just these increases that are responsible for the performance boost. nVidia’s architectural byword is ‘efficiency’, and the company claims to have redesigned and tweaked the architecture of the new card with this aim – creating what it calls the CineFX 4.0 engine.
The pixel pipelines have lower latencies, the vertex units have been rebuilt and the texture engine redesigned, fetching textures much more speedily than before. The GPU can also cull redundant pixels more efficiently than ever before. Since the introduction of programmable pixel shaders, nVidia has looked to see which were the most popular actually used by developers in actual games and has implemented these in hardware to greatly speed up their operation. The most popular shaders are multiply-add (MADD) operations, and these work twice as fast as on 6800 Ultra per pixel pipeline, which can’t be bad.
Next is a newly introduced anti-aliasing method called transparent super-sampling and multi-sampling. This enables certain things in a 3D scene that would have previously been blurred to be rendered more clearly, such as a series of wire mesh fences as seen in the opening of Half-Life 2. nVidia claims that most games should see less than ten per cent performance hit with transparent super-sampling. Borrowing a trick from ATI the new chip now supports the compression of Normal Maps at 2:1 and nVidia claims that the 3Dc compression format will work too.
But the most significant supported feature is High Dynamic Range (HDR). This is a system that applies highly realistic lighting effects and although it’s early days yet, the effect with it enabled is really quite astonishing. To give an example, when you move from a dark area into a blazingly bright area, the whole scene is filled with bright light before settling down to more even levels. But all surfaces reflect light in a way that makes a non-HDR lit scene seem quite flat by comparison. If you have the latest 1.3 patch of Far Cry it’s possible to manually enable HDR in the console.
Now technically, this isn’t actually new as it was fully supported on the 6xxx series. However, the performance delta associated with HDR enabled was so high that it was barely worth running due to low frame rates. But thanks to the speed of the new cards, it’s now a real possibility, essentially making it seem like a new feature.