Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!think.com!sdd.hp.com!mips!apple!stevec
From: stevec@Apple.COM (Steve Christensen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Strange Address Problem on Plus but not on SE/30. WHY?
Message-ID: <54278@apple.Apple.COM>
Date: 24 Jun 91 16:59:16 GMT
References: <1991Jun24.052855.29691@zip.eecs.umich.edu>
Distribution: usa
Organization: Apple Computer Inc., Cupertino, CA
Lines: 23

lagana@sparky.eecs.umich.edu (Antonio A Lagana) writes:
>I have written an INIT that among other things does a head patch to some
>toolbox routines.  I have tested it on my SE/30 and things seem to work
>fine with or without other INITs loaded (under 7.0, by the way).  However,
>when I test it on a Plus, with the same setup (with/without INITs, 7.0),
>the INIT causes the system to crash with an address error.  First of all,
>does anybody know what exactly does an "address error" mean?  Is it
>something to do with the accessed address not being aligned properly (I
>am not sure if the 68000 is word or byte addressable)?  Or is it the result
>of trying to access a memory location which does not exist?

An "address error" means that you did an unaligned access.  The 68000 won't
let you do unaligned word- or longword accesses, so you probably have a word
or longword variable that's not at least word-aligned.  The 68020 and 68030
don't care if the access is aligned or not--it could just take longer if the
processor has to read an extra long word to get the leftover piece of the
access...

steve
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Steve Christensen			Never hit a man with glasses.
  stevec@apple.com			Hit him with a baseball bat.