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From: anton@mips.complang.tuwien.ac.at (Anton Ertl)
Newsgroups: comp.arch
Subject: Re: Byte Addressability And Beyond
Date: Thu, 02 May 2024 17:37:47 GMT
Organization: Institut fuer Computersprachen, Technische Universitaet Wien
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Message-ID: <2024May2.193747@mips.complang.tuwien.ac.at>
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John Levine <johnl@taugh.com> writes:
>According to Lawrence D'Oliveiro  <ldo@nz.invalid>:
>>On Wed, 1 May 2024 01:49:56 -0000 (UTC), John Levine wrote:
>>
>>> Until the PDP-11, all byte addressed machines were bigendian. Despite a
>>> lot of looking, I have never found an explanation of why DEC made the
>>> PDP-11 littlendian.
>>
>>As I previously mentioned, little-endian just makes more sense.
>
>I happened to be looking at Blaauw and Brooks "Computer Architecture"
>published in 1997, which has several pages on bit and byte numbering.
>After noting that the Big- and Little- names come from Gulliver's
>Travels, they say on page 100:
>
> "Unlike Swift's, the computer Endian controversy is not pointless. The
> Little Endian design has many complications in use; we much prefer the
> Big Endian. Having two active conventions is very painful. Several
> recent Big Endian RISC computers, including the MIPS, the Motorola
> 88000, and the Intel i860

MIPS and 88000 support both big- and little-endian operation; and at
least for MIPS, there were a lot of little-endian machines around: the
DECstations.  Even today, <https://popcon.debian.org/> reports:

mips             : 7
mips64el         : 10
mipsel           : 4

So twice as many little-endian (el) systems as big-endian ones.

> provide a data-movement operation that can
> perform the Big Endian-Little Endian permutation. We predict that
> Little Endian addressing will die out, just as decimal addressing
> did."

I did not expect any of them to die out, but actually big-endian is
dying out.  HPPA and SPARC have been cancelled, Power has switched to
little-endian, and S390x is a niche, and MIPS has left the
general-purpose computing field.

- anton
-- 
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>