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NVIDIA GeForce 7800 GTX (G70)

By Vijay Anand - 22 Jun 2005

Vertex, Pixel, Texture Engine Updates + Longhorn Readiness

Vertex Shader Enhancements

Besides bolstering the GPU with eight vertex shader units (which now features accelerated geometry processing), the triangle setup engine following it has been speeded up to cater to the higher throughput.


Pixel Shader Enhancements

Going a rank deeper, we now touch upon the changes to the pixel shader units. Over the many months of developing their G70, NVIDIA has been carefully studying the kind of shader programs used in a wide gamut of games and identifying which kind of functions are most commonly called upon. With that information, they set out to turbo charge the shader performance with regards to these commonly used functions and of course those that NVIDIA thinks it will have strong impact in current and forthcoming games. As a result of this, they were able to crank out more performance per pipeline, per clock.

One of the areas that NVIDIA paid close attention to was Multiply + Add (MADD) operations, each of which is a 32-bit floating point operation, which are commonly found in functions such as transformations, lighting calculations, normal map calculations and others of the sort. These are highly utilized in the latest of today's games and they will be even more widely used in future games. As such, they have ensured that each of their shader units in the G70 is capable of double the MADD operations of the NV40. The latter can perform four MADDs and four MULs (multiply) operations in a single clock cycle, but the G70 can perform eight full MADD operations completely in a single clock, which is definitely a higher throughput than NV40 if you were to look at the total number of multiply and add operations required individually.

Overall, the enhancements in total have allowed the G70 architecture to boast two times the floating point shading power of the NV40 predecessor. What can we do with all this extra power? For one, you can expect future games to extensively use even more complex shader programs to recreate even better effects, High Dynamic Range lighting without reservations, as well as effectively use effects like sub-surface scattering (such as that in NVIDIA's Luna Demo). These are not really new effects as they were possible even in the GeForce 6 era, but the hardware wasn't powerful enough to use such effects effectively in large scale all the time. Perhaps high-end GeForce 6800 products may get away with such effects some of the time, but certainly not all of the GeForce 6 series.


Texture Engine Enhancements

The texture processing engine was hauled over a bit to accelerate its texture access, which is a rather immediate enhancement since textures are always used in 3D games. The improved internal cached design for the texture engine also benefits when using Anisotropic Filtering.


Designed To Support Microsoft's Longhorn OS

A year earlier when NVIDIA was launching their then new GeForce 6 series, they invited several key people from various industries who represented their respective corporations and shared with us on how their company is actively involved in shaping upcoming software that take advantage of 3D hardware. Of them, one of the most important notes was from Microsoft's Chris Donahue who shared with us information on Shader Model 3.0, as well as developments in DirectX and the next generation Longhorn operating system.

Longhorn would be somewhat different than existing Microsoft operating systems as in its core structure, the way it interacts with the user with an updated GUI, as well as supporting the new tech trends that Intel has been pushing such as virtualization and improved security. Direct3D will form the foundation (and with other technologies to form the Windows Graphics Foundation standard) of this next generation operating system, with most of what's shown onscreen being GPU driven using 3D computer graphics hardware and updated Direct3D technologies to support desktop 3D graphics, animation and other special visual effects. There will be a few user interface levels to cater for the various graphics hardware out in the market at the point of release, but for the best experience of the Avalon interface, you'll require a fairly modern 3D graphics card that is Longhorn Display Driver Model ready.

The CineFX 4.0 engine in the GeForce 7800 GTX fully supports the Windows Graphics Foundation model and has a Composited Desktop Hardware Engine to support the next generation's user interface. This engine facilitates the following effects:-

  • Video post-processing
  • Real-time desktop compositing
  • Seamlessly run multiply 3D applications
  • Accelerated antialiased text rendering
  • Special effects and animation

Expect other upcoming G70 based graphics cards to feature CineFX 4.0 and hence, would likely support the Composited Desktop Hardware Engine too for enhanced Longhorn operating system experience.

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