XSGI

Xsgi is the IRIX 4.0 and up specific X11 implementation built to replace 4Sight. It implements X11R6 standards but is highly tailored to be specific to the SGI hardware context.

Early History

Work began around 1989 when SGI hired Tom Paquin from IBM to integrate X with SGI’s IRIS GL stack. At the time, SGI was using a NeWS-based GUI for 4D1 called 4Sight. NeWS was falling out of fashion in the late 1980s and early 1990s due to its heavyweight Postscript implementation, licensing fees and speed limitations of the time. SGI previously used MEX for its GL2 systems as well as early releases of 4D1-2.x.

Architecture

SGI graphics exclusively use IRISGL/OpenGL device commands rather than the CPU writing a memory-mapped framebuffer. Xsgi therefore uses device-specific draw paths and uses GL primitives. Xsgi exposes multiple X11 visuals corresponding to SGI normal, overlay and popup framebuffers so X11 clients can target different layers (useful for GLX/IRIS GL and window system overlays).