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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: bytes, Keeping other stuff with addresses
Date: Thu, 5 Dec 2024 00:39:22 -0000 (UTC)
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Originator: johnl@iecc.com (John Levine)

According to Scott Lurndal <slp53@pacbell.net>:
>>8-bits won because it was enough (at the time of inception {IBM
>>360--1963})
>
>8-bits is also a convenient multiple of four bits, which was common
>in many machines prior to the 360.  The hardware in burroughs
>BCD machines could automatically add/remove the zone digit (bits <7:4>)
>during data movement.

Good point.  S/360 packed decimal puts two digits in each byte with the low
"digit" of the low order byte being the sign.  If they had six bit bytes, the
only other size they seriously considered, they'd either waste 1/3 of the
bits with a digit per byte, or need what would then have been an impossibly
complex encoding.

Several decades later, decimal floating point used such a complex encoding.




-- 
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