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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: Address bits again, Article on new mainframe use
Date: Wed, 11 Sep 2024 01:53:42 -0000 (UTC)
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According to Lawrence D'Oliveiro  <ldo@nz.invalid>:
>On Mon, 9 Sep 2024 16:55:44 +0000, MitchAlsup1 wrote:
>
>> With pages you can swap parts of a segment (page at a time)
>> with segmentation (only) you cannot swap parts of the segment.
>
>Mixing the two seems counterproductive, unless you have few, large 
>segments. Burroughs-style segments were smaller and more numerous than 
>that.

Multics had paged segments.  The segments were as I recall 18 bit word addressed
so about a megabyte.  The pages were perhaps 1K.  It worked pretty well.

An underappreciated advantage of paging is that the pages are all the same
size.  With variable sized segments you need to do memory shuffling to
collect the empty space into larger chunks.  The KA-10 which had two
variable sized segments per process spent a lot of time doing memory
shuffling.



-- 
Regards,
John Levine, johnl@taugh.com, Primary Perpetrator of "The Internet for Dummies",
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