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From: toddpw@tybalt.caltech.edu (Todd P. Whitesel)
Newsgroups: comp.sys.apple
Subject: Re: IIgs resolution and colors
Message-ID: <1990Mar2.215400.9392@spectre.ccsf.caltech.edu>
Date: 2 Mar 90 21:54:00 GMT
References: <2488@ttardis.UUCP> <4300@mace.cc.purdue.edu>
Sender: news@spectre.ccsf.caltech.edu
Organization: California Institute of Technology
Lines: 28

asd@mace.cc.purdue.edu (Kareth) writes:

>In article <2488@ttardis.UUCP> rlw@ttardis.UUCP (Ron Wilson) writes:

>>line of the IIgs SHR screen can be independantly assigned to any one of 16 color
>>pallets (not to mention, independant selection of the 320 and 640 modes).

>I can't claim to know a heck of a whole lot about this, but in order to
>do this (in my understanding), ya have to do all kinds of nifty
>interrupt routines and the alike.  This method is fine for just
>displaying screens, but not that great for anything useful.  Spending
>all/most of the cpu time just keeping the screen up isn't my idea of a
>workable graphics mode.

As you've mentioned, you've seen the 3200 color demos. What we're talking about
here is 256 colors (16 per palette and 16 palettes) which requires NO cpu time
once the scan line control bytes are set up{ to give the correct palette for
each screen line.

3200 colors can only be obtained by manipulating those 16 palettes while the
picture is being displayed, and that's what grabs the CPU and makes it a demo.

I repeat, you can get 16 palettes of 16 colors each and the display hardware
will take care of it for you. If you want more, then you have to resort to
special tricks.

Todd Whitesel
toddpw @ tybalt.caltech.edu