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From: mash@mips.COM (John Mashey)
Newsgroups: comp.arch
Subject: Re: Handling mis-alignment (was Re: RISC Machine Data Structure Word Alignment Problems?
Message-ID: <35488@mips.mips.COM>
Date: 4 Feb 90 19:20:11 GMT
References: <3428@odin.SGI.COM> <AGLEW.90Jan31211451@dwarfs.csg.uiuc.edu> <2038@bnr-rsc.UUCP> <1577@mipos3.intel.com>
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Reply-To: mash@mips.COM (John Mashey)
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In article <1577@mipos3.intel.com> kds@blabla.UUCP (Ken Shoemaker) writes:
>The i486 handles misaligned transfers transparently from the programming 
...
>In addition, the i486 has the ability to force traps on all misaligned
>transfers.  This lets people insure that the data structures for their

1) That's a very nice feature, like what we once asked IBM to add to S/370s.
I hope it gets plenty of use.
2) Although coming from the other direction, what MIPS does is:
	a) If you say nothing, trap misaligned references (killing process).
	b) On request, trap misalignment, and either fix them up, or
	fix them up, and keep a record of where they occurred, to help the
	user figure out what's happening.
	c) If you recompile the program and request it, the unaligned
	operations get generated.
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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