[rescue] Weird Silicon Graphics o2 graphics issues

Kevin kevin at mpcf.com
Thu Oct 2 12:09:52 CDT 2003

Cool info, makes me want to dig out my old IIgs.


On Thu, 2 Oct 2003 16:11:32 -0400 (EDT)
Nathan Raymond <nate at portents.com> wrote:
> And the Apple IIgs:
> http://www.old-computers.com/museum/computer.asp?c=71
> "320x200 with 3200 colors: in this mode, the CPU is
> used to swap palettes into and out of video memory
> such that a separate 16 color palette can be used on
> each of the 200 scan lines for 3200 possible colors.
> This mode is often used for viewing graphics...
> 640x200 with 16 dithered colors: in this mode, the
> pixels in the graphic screen are grouped into even
> and odd columns. The even columns can have a palette
> of 4 pure colors out of a of 4096 possible. The odd
> columns can have a second palette of 4 pure colors.
> The GS dithers the adjacent colors for 4x4=16
> dithered colors. This mode is widely used in
> productivity programs and also in Apple's Finder for
> the GS... Combinations and variations: the Apple IIGS
> has scan line interrupts. Part of the screen can be
> in 640x200 mode and part of it can be in 20x200
> resolution. Such split modes are sometimes used in
> paint programs, where the menu bar is in 640x200
> while the graphic is in 320x200."

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