Path: utzoo!attcan!uunet!aplcen!haven!mimsy!mojo!russotto
From: russotto@eng.umd.edu (Matthew T. Russotto)
Newsgroups: comp.sys.mac.hardware
Subject: Re: SE/30 -> 32 bit clean ROMS?
Message-ID: <1990Oct26.044933.14314@eng.umd.edu>
Date: 26 Oct 90 04:49:33 GMT
References: <2562@ux.acs.umn.edu>
Sender: news@eng.umd.edu (The News System)
Organization: College of Engineering, Maryversity of Uniland, College Park
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In article <2562@ux.acs.umn.edu> dhoyt@vx.acs.umn.edu writes:
>In article <1990Oct25.183759.10653@eng.umd.edu>, russotto@eng.umd.edu (Matthew T. Russotto) writes...
>>Patching the memory manager 'on the fly' would be impossible-- you would end up
>>invalidating the structures in the system heap.
> I may be mistaken on this, but I believe that Virtual from Connectix
>accomplishes something very near this.  If they can make MacOS think that there
>is 14 MB of memory when in fact there are only 5, it doesn't seem unlikely that
>Apple could patch the memory manager to be 32 bit clean.


Virtual 'merely' remaps some of the nubus memory to be continuous with the
main memory, and changes system structures to let the system know how
big memory now is. (it also implements virtual memory-- in fact, that's
the MAIN reason for it).  Neither of these actions in any way invalidates
EXISTING handles to the system and application heap.  Switching to a 32
bit memory manger on the fly would be many, many, orders of magnitude more
difficult, as this would require Apple to somehow preserve the validity
of the unclean master pointers in the system heap while also making them
clean-- not an enviable task.  Doing it by doing a near full restart
would be easier, but still not an enviable task.  (this is how A/UX does it--
it entirely destroys the mac environment and creates a new one from scratch)
--
Matthew T. Russotto	russotto@eng.umd.edu	russotto@wam.umd.edu
Tax the rich, and feed the poor -- until there are, rich no more.