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Path: utzoo!watmath!clyde!rutgers!mit-eddie!husc6!seismo!mimsy!eneevax!hsu
From: hsu@eneevax.UUCP
Newsgroups: comp.sys.apple
Subject: Re: Applevision (I was wrong, almost)
Message-ID: <661@eneevax.UUCP>
Date: Mon, 16-Feb-87 10:42:40 EST
Article-I.D.: eneevax.661
Posted: Mon Feb 16 10:42:40 1987
Date-Received: Wed, 18-Feb-87 06:17:46 EST
References: <890@ihlpm.UUCP> <875@sdcc7.ucsd.EDU>
Reply-To: hsu@eneevax.UUCP (Dave Hsu)
Organization: The Royal Maryland Ice Cream Consumption Laboratory
Lines: 25

In article <875@sdcc7.ucsd.EDU> ln63wzb@sdcc7.ucsd.edu.UUCP (Grobbins) writes:
>
>Bob Bishop did publish an article on how to flip pages to mix text
>and graphics.  But since his sample programs did it with timing
>loops not tied to the redrawing of the screen, flicker was horrible.
>He didn't have any choice; no information on the state of the video
>circuitry is available to software in the Apple II and II+.

Actually, I seem to remember somebody publishing a technique that kept
staring at a supposedly unimportant address, watching for some sequence
(something like three `04's and something else) and flipping THEN.
Never did look at it closely enough to see how it worked.

>Does the //e allow software to detect the video retrace situation?
>If so, has anyone used it to mix text/lo-res/hi-res lines on the
>screen?
>
>Grobbins

There is a retrace flag available; no, I don't remember the address.

-dave
-- 
David "bd" Hsu	hsu@eneevax.umd.edu <or> seismo!mimsy!eneevax!hsu
EE Computer Facility, Maryversity of Uniland, College Park, MD 20742