While the T&L module can easily cope with this seemingly endless stream of triangles, other system components have lower limits. The AGP bus is currently designed for a maximum of one gigabyte per second (AGP 4X) and also has to cope with transporting unwieldy textures. The system memory offers only one gigabyte per second and must use this to serve all the PC’s components, including the CPU. There is often less than 0.4 GB/s left over for reading geometrical data.
And a taste of things to come.
The next big technological leap is programmable T&L. At present, developers can choose to use pre-programmed functions or to ignore them. In future they will be able to adapt functions to their own requirements by loading small programs onto the 3D card. The feature, called a “vertex shader”, is a major new aspect of DirectX8 (on our disc by the way) and Nvidia’s next generation of chips to be used in Xbox (and probably PC cards), called the NV20.