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From: seah@ee.rochester.edu (David Seah)
Newsgroups: comp.sys.apple2
Subject: Re: Stellar 7 re-release
Message-ID: <1991Jan5.001047.4602@ee.rochester.edu>
Date: 5 Jan 91 00:10:47 GMT
References: <60237@microsoft.UUCP> <1991Jan3.065643.24082@nntp-server.caltech.edu> <10019@pasteur.Berkeley.EDU>
Organization: University of Rochester Department of Electrical Engineering
Lines: 18

In article <10019@pasteur.Berkeley.EDU> benji@euler.Berkeley.EDU (Benji Rudiak-Gould) writes:
>Then why are 3200-color pictures called that?  If you can only have an
>interrupt every other line, say, then the most that can be managed is 1600
>colors.  Dreamgraphix is doing something besides just displaying the
>picture, so I can see the problem there, but an ordinary display program
>should be able to get all 3200 colors.

You don't need to use an interrupt on every scanline...your program
can track the vertical scanline counter register (documented in
an Apple IIGS technote I don't have handy) to figure out when to change.
One could also use all 16 hardware-supported palettes and update them
every 16 scanlines, which might buy you some extra CPU to do something
useful other than synchronize to the electron beam.
-- 
Dave Seah ^..^  |  Analog Design Automation Research Group - Graphics & GUI  | 
                |  University of Rochester, Dept. of Electrical Engineering  |

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