Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!uunet!comp.vuw.ac.nz!actrix!amiga!twills
From: twills@amiga.actrix.gen.nz (Tony Wills)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Amiga Custom Chips - why hasn't C= made them faster?
Message-ID: <6154.tnews@amiga.actrix.gen.nz>
Date: 12 Apr 91 02:05:20 GMT
Followup-To: comp.sys.amiga.hardware
Organization: NZAmigaUG.
Lines: 46

Quoted from - tagreen@bronze.ucs.indiana.edu (Todd A. Green):
> In article <1991Apr5.034303.14202@engin.umich.edu> milamber@caen.engin.umich.edu (Daryl Scott Cantrell) writes:
[...]
> >Virtual memory comes to mind as a far more productive use for the MMU.  Can
> >you say 100 MB free? [insert drool noise]  Not to mention color X-Windows
> 
> Can you say let's watch this window get paged in from disk? [insert
> yawn noise here].  Have you ever used virtual memory on a system with
[...]
> My point is that VM is nice, VM is good, VM is your friend, but it
> ain't never gonna nohow replace RAM.

I certainly agree that the Amiga I/O etc is a little slow for virtual memory
if you considered swapping tasks (or just code/data 'pages') in and out during
task switching.

I envisage using virtual memory principles to allow me to swap out complete
Amiga programs, ie take the code, data, and current register state, and stuff
them onto disk thus freeing up memory, but allowing the program to continue at
a later time from where it left off.
(Of course if the program isn't self modifying no need to copy it to disk)

A major problem with this idea is the Amigas lack of resource tracking, ie
you don't know which bits of memory belong to which task.  But then I
suppose you can just intercept the memory allocation system calls, and
keep your own resource table - retrofit resource tracking :-(

Why would I want to do this ? (manually switch out tasks), I was thinking
of things like raytracing and mandelbrots, which take a lot of processing
time, and consume memory all that while - if I could swap them out, freeing
up my whole machine temporarily for other large, short lived, tasks it
would improve my productivity.
If you switched out more information (like system task table entries, and
any other info required by the operating system about executing tasks), you
could even swap out tasks and switch off the machine ... then resurect them
later to continue as though nothing had happened!

This would be a non trivial operating system hack, it'd be easier just to
purchase a 100 Megs!! :-)
--
      _
    o(_)  (c) Tony Wills 19**  | All the world should live in alt.folklore,
   /  /\  twills@actrix.gen.nz |    unfortunately some die in sci.skeptic
               NZAmigaUG       |                                  -AJW 1991