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From: carolyn@cbmvax.cbm.UUCP (Carolyn Scheppner CATS)
Newsgroups: comp.sys.amiga
Subject: Re: Aminetics ram + graphics bug.
Message-ID: <1892@cbmvax.cbmvax.cbm.UUCP>
Date: Mon, 18-May-87 13:17:42 EDT
Article-I.D.: cbmvax.1892
Posted: Mon May 18 13:17:42 1987
Date-Received: Tue, 19-May-87 04:06:35 EDT
References: <57@f.gp.cs.cmu.edu>
Reply-To: carolyn@cbmvax.UUCP (Carolyn Scheppner CATS)
Organization: Commodore Technology, West Chester, PA
Lines: 32

In article <57@f.gp.cs.cmu.edu> mjw@f.gp.cs.cmu.edu (Michael Witbrock) writes:
>I have a problem with my computer. On two particularly hairy grapohics
>programs (MCAD12 and Jugglerdemo), a stripy (every second horizontal pixel
>(plus a few others)) pattern SOMETIMES appears about 3/4 of the way across
>my screen. It is about 2-3cm wide, and takes up the lower third or twothirds
>of the screen (sometimes the full height as well). 
>
>As far as I can tell (paranoid look crosses face), this problem affects
>nothing else. This problem has started to occur since I installed the
>aminetics board.

   What you are seeing is the infamous SetPointer() to an array of zeros
(or whatevers) declared within the program.  By default, the hunks of
an executable are marked to load into MEMF_PUBLIC memory.  If there
is FAST ram available, the hunks will be loaded there (saving your
valuable CHIP memory for screens, etc.).  So... If the PROGRAM is loaded
into FAST mem, so is the array containing the new image for the pointer.
And the custom chips can not access it there so they end up seeing
some other memory totally unsuitable as a sprite definition.

   The first released version of the Juggler had this problem.  The later
release (also on a Fish disk) should not.  The usual fixes for executables
with similar problems are either run FixHunk on them (marks DATA hunks
for CHIP load) or use a utility that disables or hides FAST ram before
loading the program.

-- 
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Carolyn Scheppner -- CBM   >>Amiga Technical Support<<
                     UUCP  ...{allegra,caip,ihnp4,seismo}!cbmvax!carolyn 
                     PHONE 215-431-9180
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