Core Architecture Changes

So what makes this a new generation?

Scott then spent some time outlining for us the specific differences between V3 and VSA-100, as well as the special modifications and feature sets added to the latter.

Best case Voodoo4 vs. Voodoo3

3dfx feature list

First off, VSA-100 supports full AGP 4X with sidebanding. Without getting into AGP texturing, the higher bandwidth and faster transfer rate of AGP4X allows more data, specifically triangle/polygon information, to be sent down the pipeline, eliminating the system bus as a bottleneck to performance.

Whereas the Voodoo3 supported a maximum of 16MB local memory, each VSA-100 processor can support up to 64MB of RAM. While no consumer card has yet shipped with more than 32MB, 64MB should start becoming standard (if for nothing more than just a large bullet point on the retail packaging) within the next generation of 3D accelerator.

VSA-100 supports true 32-bit RGBA final color rendering, as well as full 24-bit depth buffering consisting of Z and W buffers. Voodoo3 of course, was heavily based on the prior Voodoo technologies, and only supported final output in 16-bit color. Also, while the Voodoo3 also supported fixed or floating point Z/W, these were only 16-bit. W-buffer information is primarily used for perspective-correction on textures, and since the information is sent down regardless, it can also be used for overdraw protection (generally known as Z-buffering). If developers begin using the W-buffer instead, it's possible to save the bandwidth needed to send Z information down the pipe as well. VSA-100 also supports a standard 8-bit stencil buffer, for all of the stencil-buffer shadows supported in today's OpenGL and Direct3D games.

A slightly obscure feature added is the ability to selectively write to individual color RGBA color channels, in order to maintain tighter OpenGL compatibility. It looks like 3dfx is making a concerted effort to embrace full OpenGL, rather than the "miniGL" implementations used solely for Quake-type games. In addition is a revamping of the method colors and textures are combined, which in Voodoo3 wasn't 100% compliant with the OpenGX Multitexture extension.

More optimizations

In addition, a significant modification was made to the DirectX 6/7 pixel pipeline, which has the potential to slightly increase performance on certain multipass operations, which can now be rendered in a single pass. New alpha-blending capabilities have also been added to the VSA-100 hardware, with support for specific modulation, and subtractive blending. Extensions to support these new capabilities will be available for Direct3D and OpenGL, but Glide support is currently TBD.

Of course, with 32-bit texture support, VSA-100 also supports true 32-bit RGBA color textures, and large (2048x2048) texture maps. As with Voodoo3, support is also implemented for rectilinear (non-square) textures, a must for any 3D card supporting large textures. VSA-100 also supports various modes of texture compression including narrow channel compression (NCC), all five modes of DXTC (S3 texture compression), and FXT1, 3dfx's open-source compression algorithm.

But what about the really big changes?