Path: utzoo!attcan!uunet!cs.utexas.edu!tut.cis.ohio-state.edu!rutgers!cmcl2!ccnysci!alexis
From: alexis@ccnysci.UUCP (Alexis Rosen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: System 7.0 Q & A
Keywords: Low Memory Globals
Message-ID: <2086@ccnysci.UUCP>
Date: 24 May 89 11:57:02 GMT
Reply-To: alexis@ccnysci.UUCP (Alexis Rosen)
Organization: City College of New York
Lines: 34


I've been watching this discussion for a while, but nobody seems to have
come up with this, so...

The arguments about why we can't have complete memory protection are fairly
convincing (disgusting perhaps, but convincing).  This doesn't address why we
can't have preemptive multitasking, but there are surely other good reasons
for this lack. I would like something much simpler- so simple that it would
probably take hours, or a few days at most, for someone doing OS work at Apple,
but so integrally liked to the OS that it would probably be impossible for
anyone else to do.

Why can't we have a little program that takes a chunk of memory and boots a
new Mac inside of this memory? In fact, you could probably boot System 6.0
on this virtual Mac, but I won't push things. (You could probably also run it
in 24-bit mode while leaving the rest in 32-bit mode.) This would solve all of
the compatability problems with one stroke.

Actually there are a few gotchas, but I don't see them as major problems. The
primary difficulty that I can see is that the disk drive may be altered by
one virtual Mac and the other would get confused. But since Apple has their
personal AppleShare code nearly done, they could simply install the appropriate
External File System in the new virtual Mac so that it would think its disk
was being shared. This way any alterations to the disk would be dealt with
properly.


To be honest, I'm surprised that Connetix hasn't offered multiple "virtual
Macs" as a feature of their product already.

---
Alexis Rosen
alexis@ccnysci.{uucp,bitnet}
alexis@rascal.ics.utexas.edu  (last resort)