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From: c160-1bj%holden@UCBVAX (Courtney Goeltzenleuchter)
Newsgroups: net.micro.atari
Subject: Re: Modified Display Lists
Message-ID: <8511260537.AA22287@ucbholden>
Date: Tue, 26-Nov-85 00:37:28 EST
Article-I.D.: ucbholde.8511260537.AA22287
Posted: Tue Nov 26 00:37:28 1985
Date-Received: Wed, 27-Nov-85 06:18:07 EST
References: <8511252100.AA22014@ucbvax.berkeley.edu>
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Organization: University of California, Berkeley
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Hi, you've probably already got a dozen answers on this one, but since I know
the answer I thought I'd throw in my two cents worth.
   The Atari OS stores the location of the display list in locations 560, 561
(decimal usual low, high format).  Every 60th of a second a vertical blank
interupt is generated and this 'shadow' value is put into 54274, 54275 which
tells the hardware to really find the display list.  So, in effect, it makes
the last instruction almost useless, the only thing it does is tell the hardware
to stop sending stuff to the screen.  In other words if you want to change whereyour display list is located you'll have to chage the 'shadow' memory.
If you want to know ALL about the Atari 800 and related computers your best
bet is the book "De Re Atari" it's just packed with useful info.
Well I hope this answered you question.  Have fun.
		-Courtney Goeltzenleuchter
		-- c160-1bj@holden@BERKENLEY.EDU