Intel® 865G/865GV Chipset Datasheet - download.intel.nl - Intel

Functional Description5.4.1 3D EngineThe 3D engine of the GMCH has been designed with a deep pipelined architecture, whereperformance is maximized by allowing each stage of the pipeline to simultaneously operate ondifferent primitives or portions of the same primitive. The GMCH supports perspective-correcttexture mapping, multitextures, bump-mapping, cubic environment maps, bilinear, trilinear andanisotropic MIP mapped filtering, Gouraud shading, alpha-blending, vertex and per pixel fog andZ/W buffering.The 3D pipeline subsystem performs the 3D rendering acceleration. The main blocks of thepipeline are the setup engine, scan converter, texture pipeline, and raster pipeline. A typicalprogramming sequence would be to send instructions to set the state of the pipeline followed byrending instructions containing 3D primitive vertex data.The engines’ performance is dependent on the memory bandwidth available. Systems that havemore bandwidth available will significantly outperform systems with less bandwidth. The engines’performance is also dependent on the core clock frequency. The higher the frequency, the moredata is processed.5.4.1.1 Setup EngineThe setup stage of the pipeline takes the input data associated with each vertex of a 3D primitiveand computes the various parameters required for scan conversion. In formatting this data, GMCHmaintains sub-pixel accuracy.3D Primitives and Data Formats SupportThe 3D primitives rendered by GMCH are points, lines, discrete triangles, line strips, trianglestrips, triangle fans and polygons. In addition to this, GMCH supports the Microsoft DirectX*Flexible Vertex Format (FVF), which enables the application to specify a variable length ofparameter list obviating the need for sending unused information to the hardware. Strips, Fans, andIndexed Vertices, as well as FVF, improves delivered vertex rate to the setup engine significantly.Pixel Accurate “Fast” Scissoring and Clipping OperationThe GMCH supports 2D clipping to a scissor rectangle within the drawing window. Objects areclipped to the scissor rectangle, avoiding processing pixels that fall outside the rectangle. GMCH’sclipping and scissoring in hardware reduce the need for software to clip objects, and thus improvesperformance. During the setup stage, the GMCH clips objects to the scissor window.A scissor rectangle accelerates the clipping process by allowing the driver to clip to a bigger regionthan the hardware renders to. The scissor rectangle needs to be pixel accurate, and independent ofline and point width. The GMCH supports a single scissor box rectangle that can be enabled ordisabled. The rectangle is defined as an Inclusive box. Inclusive is defined as “draw the pixel if it isinside the scissor rectangle”.Intel ® 82865G/82865GV GMCH Datasheet 165