Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!cbmvax!valentin
From: valentin@cbmvax.commodore.com (Valentin Pepelea)
Newsgroups: comp.sys.amiga.tech
Subject: Re: MMU + A3000 + AmigaOS2.0 == Non-crashing system?
Message-ID: <13625@cbmvax.commodore.com>
Date: 4 Aug 90 03:00:50 GMT
References: <2489@clinet.FI> <20889@grebyn.com> <6405@wolfen.cc.uow.oz> <20927@grebyn.com>
Reply-To: valentin@cbmvax (Valentin Pepelea)
Organization: Commodore, West Chester, PA
Lines: 33

In article <20927@grebyn.com> ckp@grebyn.UUCP (Checkpoint Technologies) writes:
>
> I think this is grand.  In fact, Commodore seems to be planning this,
> because they already have plans to implement Virtual Memory.
> Unfortunately VM does not necessarily imply "protection". It offers only
> a larger virtual memory area than available physical memory provides.
>
> My definition of "Protection": Where each program has a unique
> virtual address space, and where the address space of all other programs
> is unaddressable, except in such case that two tasks formally agree to
> share some memory space and make this known to the OS.

Actually, memory protection and separate adress spaces are two different
concepts, just like virtual memory is distinct from memory protection.
If memory protection is implemented on the Amiga, then all tasks will have to
share the common 4 Gig adress space. All tasks would be allowed to read each
other's memory, but would be allowed to write only to specifically permitted
memory.

Due to the popularity of Unix, we are tempted to understand operating system
concepts in terms of how Unix has been implemented. It is very difficult to
convince a programmer that a global addressing space is much more efficient
and versatile than a separate addressing spaces as implemented in Unix. The
history of hardware capabilities have limited the memory model of Unix to
what we are familiar with now, and that is likely to limit the intellectual
capabilites of programmers for years to come.

Valentin
-- 
The Goddess of democracy? "The tyrants     Name:    Valentin Pepelea
may distroy a statue,  but they cannot     Phone:   (215) 431-9327
kill a god."                               UseNet:  cbmvax!valentin@uunet.uu.net
             - Ancient Chinese Proverb     Claimer: I not Commodore spokesman be