Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!decwrl!public!valentin
From: valentin@public.BTR.COM (Valentin Pepelea)
Newsgroups: comp.sys.amiga.programmer
Subject: Re: Virtual Memory Program?
Message-ID: <1985@public.BTR.COM>
Date: 2 Mar 91 08:19:30 GMT
References: <1991Feb14.193510.13772@bradley.bradley.edu> <%1+-SC%@irie.ais.org> <91050.163512GHGAQZ4@cc1.kuleuven.ac.be>
Organization: BTR Communications, Mtn. View, CA
Lines: 47

In article <91050.163512GHGAQZ4@cc1.kuleuven.ac.be>
GHGAQZ4@cc1.kuleuven.ac.be writes:
>
>I've written a routine to list the MMU tree (for my debugger).
>The problem is that this routine works in AmigaDOS 2.0 (on my Amiga 3000)
>but not in AmigaDOS 1.3. The routine simply thinks that the list is
>infinite. The problem could be that my routine does not support all
>MMU features. For example, I do not support page indirection, 8 BYTE
>pages, FC code tables. I'm pretty sure that AmigaDOS 1.3 does NOT use
>8 BYTE pages and FC code tables so I think the problem is with the
>page indirection feature of the MMU.

The 2.0 and 1.3 translation trees used by the A3000's SuperKickstart are
identical. In both cases the first level of the tree is limited to 16
entries by the limit field of the CRP. Well, that's how things used to be
in the summer of 1990. I haven't bothered to check since.

> Has anyone in AmigaLand some source
> to do things with the MMU that he/she wants to share with me ?
> I'm especially interested in a complete MMU table lister.

I have written an utility which does exactly this in my spare time, but while
at the employ of Commodore-Amiga. It was quite interesting to see the
progression of the translation tree used by SuperKickstart from the early
days to its final stages. If you beg hard enough, perhaps the people at C-A
will start distributing the thing.

Otherwise, the only freely distributable thingy would be Dave Haynie's
SetCpu program. The latest version is 1.6, but if you want to understand
the source code, go back to 1.4.

> If I get a lot of response I even might write a virtual memory system
> for the Amiga :-)

Sorry, but you've been preempted. I implemented virtual memory for the
Amiga as a fourth year university project, back in 1989. You are still
welcome to try your own hand at it, but if you have my luck, you'll
run into a multitude of compiler bugs, assembler bugs and operating system
bugs. Unless you are motivated by the granting of a four year degree upon
completion of your project, you are likely to loose motivation.

Valentin
-- 
"An operating system without virtual memory      Name:      Valentin Pepelea
 is an operating system without virtue."         Phone:     (408) 985-1700
                                                 Usenet:    mips!btr!valentin
                     - Ancient Inca Proverb      Internet:  valentin@btr.com