Developing the GX graphics accelerator architecture

A novel approach to acceleration is described whereby high-level graphics on entry-level workstations has become practical. In the GX, the host CPU functions as the intelligent controller and two large ASICs (application-specific ICs) supply hardwired graphics functions. An arbitrary quadrilateral is the GX´s only geometric primitive. However, it can readily approximate circle and arc primitives with short line segments. In addition, the GX supports flat shading of images only when every pixel on a polygon is the same color or intensity. However, by breaking the object into many smaller objects (tessellation), each with its own color, users can obtain a visually acceptable approximation to Gouraud-shading techniques. A description is given of the frame buffer chip and its graphic attributes and of the transformation engine and cursor chip. The chips do not have the complex instructions found in CISC (complex-instruction-set-computer) processors; rather, they perform the equivalent of very complicated software subroutines. The high speed and scalable performance of the GX and its software interface are discussed.<>