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From: John Levine <johnl@taugh.com>
Newsgroups: comp.arch
Subject: Re: base hackery, Why I've Dropped In
Date: Sun, 15 Jun 2025 17:22:09 -0000 (UTC)
Organization: Taughannock Networks
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Cleverness: some
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Originator: johnl@iecc.com (John Levine)

According to Stephen Fuld  <sfuld@alumni.cmu.edu.invalid>:
>> So IBM could have created a time-sharing operating system that ran on
>> models of the System/360 other than the model 67 with its Dynamic
>> Address Translation hardware as follows: ...

I gather that APL\360 more or less did that. The user's data block was addressed
from a specific base register, the interpreter could only be preempted at
specific points, where the monitor was allowed to move the data block and adjust
the base register. Any pointers within the data block were relative, and
addresses always computed relative to the base register. I imagine the 360's RX
addressing with both base and index registers came in handy.  There was only
one copy of the interpreter code which never moved.

It worked well but depended on very disciplined application programming.

-- 
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