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From: bazyar@ernie (Jawaid Bazyar)
Newsgroups: comp.sys.apple2
Subject: Re: Video Overlay Card software?
Keywords: Apple IIGS video overlay software wanted
Message-ID: <1991Jan13.183317.28788@ux1.cso.uiuc.edu>
Date: 13 Jan 91 18:33:17 GMT
References: <14833@smoke.brl.mil> <1991Jan13.062844.26145@nntp-server.caltech.edu>
Sender: news@ux1.cso.uiuc.edu (News)
Reply-To: bazyar@cs.uiuc.edu
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In article <1991Jan13.062844.26145@nntp-server.caltech.edu> toddpw@nntp-server.caltech.edu (Todd P. Whitesel) writes:
>Why it crashes: the extra video memory is an exact copy (scbs & palettes too)
>-- a SHR page two -- in bank $e0. Unfortunately, GS/OS allocates space for
>handle structures at $e0/6000 (right in the middle of the screen) early on
>in the boot process (i.e. before any inits are loaded). I have a P8 program
>that allocates a fixed non-purgable 16K block at $e0/6000 and manually changes
>its user ID to zero (this is illegal, but otherwise the block will be nuked
>when the O/S boots). It must be run before booting GS/OS. (Thanks to John
>MacLean for the tip! I told Dan, hopefully he'll rail on the GS/OS people about
>it. 5.0.4 still puts handles at $e0/6000.)

  It always bugged me severely that Apple chose to put memory management
data structures in SLOW RAM. And chose to put the super hi res buffers
in slow ram.  And other, seemingly brain dead design decisions.
  Not the way to build a computer, in my book.
  Someone will just have to do it better ;-)

--
Jawaid Bazyar               | Being is Mathematics 
Senior/Computer Engineering | Love is Chemistry
bazyar@cs.uiuc.edu          | Sex is Physics
   Apple II Forever!        | Babies are engineering