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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: Byte Addressability And Beyond
Date: Thu, 2 May 2024 11:52:56 -0000 (UTC)
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According to Lawrence D'Oliveiro  <ldo@nz.invalid>:
>Sure. Consider this pseudo-assembly-language sequence:
>
>    move.l a, b
>    move.b b, c
> ...
>Now the question is: which byte from “a” ends up at location “c”?

You really should stop guessing about computer architectures rather
than reading up on them.

On S/360, which is the ur-big-endian machine, memory to memory moves
are different from register loads and stores.  There are ICM and STCM
instructions that take a four bit mask to say which bytes in the
register to load or store.  There are also IC and STC for the common
case that you only want to load or store the low byte.

>In other words, even on big-endian architectures, registers are still 
>interpreted as little-endian!
>
>Isn’t that fun?

I suppose it would be if it were true.


-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly