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From: mash@mips.com (John Mashey)
Newsgroups: comp.arch
Subject: Re: Segmented Architectures ( formerly Re: 48-bit computers)
Message-ID: <1654@spim.mips.COM>
Date: 30 Mar 91 22:57:47 GMT
References: <1991Mar27.172325.10800@sj.nec.com> <1991Mar29.011956.2801393@locus.com>
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In article <1991Mar29.011956.2801393@locus.com> dana@locus.com (Dana H. Myers) writes:
...
>   The segmented vs. linear addressing architecture argument is moot.
>Changes in the 80386 allow one to effectively ignore the segments and
>use linear addresses.
>
>     System V/386 does this, AIX-PS/2 does this, etc.
>
>  Further overzealous condemnation of Intel CPUs is pointless and
>rhetorical, especially given that Intel has left the segmented architecture
>behind in the 1980's. The 80860 and 80960 are, functionally speaking, not
>segmented machines.

Well, not quite.  People shifted to 32-bit flat as soon as they could on the
386/486, but the chips clearly include a 48-bit (16+32) segmented
address scheme as well.  Here are a few interesting questions:
	1) Does any software in common use actually make use of the
	segmentation to get significantly more than 32-bit addresses?
	(i.e., I mean more than, perhaps, dedicating a segment to code
	and one to data, and maybe one to stack?
	[I hope to get answers to this one.]
	2) The 586 is reputed to be a 64-bit architecture.  Does this
	mean that the 16+32 scheme is abandoned, or that it is inclued along
	with >32-bit flat addressing?
	[I don't expect an answer on that; it is an interesting question.]
-- 
-john mashey	DISCLAIMER: <generic disclaimer, I speak for me only, etc>
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