SunOS 5 had the DGA library, which provided device independent access to the different cg[3,6,14], TCX or LEO graphics adapters, which also was the thing which supported DOOM on the SPARC machines.

cg6 was a 8 bit, usually used in X11 as a pseudocolor visual but it could also provide an 8 bit truecolor while the tcx and leo is 24 bit accelerated 3d display frame buffers (pseudocolor = a byte in videoram is an index into a large table which gives an 3x8 RGB value, and the table's content can be changed easily.) The cg3 had about the same ability but it wasn't accelerted (the cg6 designers started afterwards another firm ... nVidia.)

The later devices like the PGX which was based on ATI Rage Pro chipset couldn't support truecolor and pseudocolor at the same time, which the earlier ones did. This forced a user to choose between old applications written for the pseudocolor model (or upgrade the sw if possible) and running only truecolor oriented apps.

Pseudocolor existed basically because what was videoram was awfully expensive in the mid 80s until 1992 or so. A color display which supported an usuable workstation type resolution was also rather expensive (the 1984 Sun 2 black and white had a resolution of 1152x864 while a 1989 or so MG1 had 1600x1280 but b&w.)

I write this because i want to show the different requirements which X11 had to support.

SunOS 5 had the DGA library, which provided device independent access to the different cg[3,6,14], TCX or LEO graphics adapters, which also was the thing which supported DOOM on the SPARC machines.

cg6 was a 8 bit, usually used in X11 as a pseudocolor visual but it could also provide an 8 bit truecolor while the tcx and leo is a 24 bit accelerated 3d display frame buffer (pseudocolor = a byte in videoram is an index into a large table which gives an 3x8 RGB value, the table's content can be changed easily.) The cg3 had about the same ability but it wasn't accelerated (the cg6 designers started afterwards another firm ... nVidia.)

The later devices like the PGX which was based on ATI Rage Pro chipset couldn't support truecolor and pseudocolor at the same time, which the earlier ones did. This forced a user to choose between old applications written for the pseudocolor model (or upgrade the sw if possible) and running only truecolor oriented apps.

Pseudocolor existed basically because what was videoram was awfully expensive in the mid 80s until 1992 or so. A color display which supported an usable workstation type resolution was also rather expensive (the 1984 Sun 2 black and white had a resolution of 1152x864 while a 1989 or so MG1 had 1600x1280 but b&w.)

I write this because i want to show the different requirements which X11 had to support.