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From: rhialto@cs.kun.nl (Olaf'Rhialto'Seibert)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Virtual Memory Program?
Message-ID: <2806@wn1.sci.kun.nl>
Date: 6 Mar 91 10:02:20 GMT
References: <%1+-SC%@irie.ais.org> <1991Feb20.175103.24611@jato.jpl.nasa.gov> <1986@public.BTR.COM>
Sender: root@sci.kun.nl
Organization: University of Nijmegen, The Netherlands
Lines: 25

In article <1986@public.BTR.COM> valentin@public.BTR.COM (Valentin Pepelea) writes:
>Obviously, DMAing into virtual memory is not possible without the full
>support and knowledge of the operating system. But then, I don't know
>of any operating system offering the possibility of DMAing into virtual
>memory. No wonder considering the futility of such an exercise.

IBM, in its infinite wisdom, does this (sort of) with VM/CP (Virtual
Machine/ Control Program) for 370-style mainframes. Basically, VM
emulates complete (totally complete) 370 machines on 370s (or anything
compatible). That means: you can do all I/O a 370 can, which usually
means DMA into virtual memory (since the whole machine is virtual).
Therefore you have virtual disks, virtual printers, and (yeah) virtual
card readers and punches for communication with the outside world.
Sending a file means punching it, while spooling the virtual cards to a
special machine (RSCS) which sends the file to another machine or across
a network. And you can define new devices with a simple command.

Interesting concept. Very complex. Hopelessly outdated, but very
interesting. The source listing to a very old version of VM was about
one meter high, all written in assembly.

>Valentin
--
Olaf 'Rhialto' Seibert                               rhialto@cs.kun.nl
How can you be so stupid if you're identical to me? -Robert Silverberg