Path: ...!news.misty.com!news.iecc.com!.POSTED.news.iecc.com!not-for-mail
From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: branch address architecture, not interactive use, The Design of
 Design
Date: Sun, 12 May 2024 22:21:37 -0000 (UTC)
Organization: Taughannock Networks
Message-ID: <v1rfdh$1jm3$1@gal.iecc.com>
References: <v03uh5$gbd5$1@dont-email.me> <v1n5an$1teo9$1@dont-email.me> <v1olut$1q8p$1@gal.iecc.com> <v1q891$2ml5d$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit
Injection-Date: Sun, 12 May 2024 22:21:37 -0000 (UTC)
Injection-Info: gal.iecc.com; posting-host="news.iecc.com:2001:470:1f07:1126:0:676f:7373:6970";
	logging-data="52931"; mail-complaints-to="abuse@iecc.com"
In-Reply-To: <v03uh5$gbd5$1@dont-email.me> <v1n5an$1teo9$1@dont-email.me> <v1olut$1q8p$1@gal.iecc.com> <v1q891$2ml5d$1@dont-email.me>
Cleverness: some
X-Newsreader: trn 4.0-test77 (Sep 1, 2010)
Originator: johnl@iecc.com (John Levine)
Bytes: 2004
Lines: 21

According to Thomas Koenig  <tkoenig@netcologne.de>:
>John Levine <johnl@taugh.com> schrieb:
>
>> Do we know who invented relative branches? The PDP-11 had them in 1969
>> but I don't think they were new then.
>
>Very good question.

Flipping through the machine descriptions in Blaauw and Brooks, I see
that the B5500 had relative addressing as one of its gazillion address
modes, which was quite possibly the first time they were used.  But I
would not count on the PDP-11 designers being aware of that.

The page addressing on the PDP-8 is a pain since you have to divide
your code into little blocks of the right size to make it work.
Relative branching on the PDP-11 let them keep small branch addresses
but not force the memor into pages.

-- 
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