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From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.mac.programmer
Subject: Re: SwapMMUMode? or GetPixBaseAddr?
Message-ID: <1990Nov28.042555.7407@eng.umd.edu>
Date: 28 Nov 90 04:25:55 GMT
References: <77758@ipl.jpl.nasa.gov>
Sender: news@eng.umd.edu (C-News)
Organization: College of Engineering, Maryversity of Uniland, College Park
Lines: 18

In article <77758@ipl.jpl.nasa.gov> mkt059@ipl.jpl.nasa.gov (Mike Tschudi (Cartographic Applic.)) writes:
>Has anyone had experience with SwapMMUMode or 32-bit QuickDraw's
>GetPixBaseAddr?
>
>I'd like to alter the values of pixels in an offscreen GWorld, but
>GetPixBaseAddr says that it returns a 32-bit pointer that is the
>only way to get to the offscreen GWorld's PixMap, and SwapMMUMode
>crashes my Mac (IIcx using Think C 4).

There is a tech note on this-- what happens is the PC looks like this:
XXYYYYYY, so when you swapMMUMode, those XXs cause the machine to go
off into lala land and crash.  You need a bit of inline assembly to
fix the PC so it looks like 00YYYYYY before you call SwapMMUMode.


--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
     .sig under construction, like the rest of this campus.