Path: utzoo!attcan!uunet!cbmvax!daveh
From: daveh@cbmvax.UUCP (Dave Haynie)
Newsgroups: comp.sys.amiga.tech
Subject: Re: MMU in 2620/Macintosh emulation
Message-ID: <5819@cbmvax.UUCP>
Date: 26 Jan 89 21:09:12 GMT
References: <7338@netnews.upenn.edu>
Organization: Commodore Technology, West Chester, PA
Lines: 27

in article <7338@netnews.upenn.edu>, ranjit@eniac.seas.upenn.edu (Ranjit Bhatnagar) says:
> Summary: Can the MMU create an independent address space for Mac tasks?
> Beverage: Dr. Pepper

> I was wondering - does the MMU in the 2620 do address remapping,
> or just protection?  

The 68851 does both translation and protection.

> If the former, could it be used to give a nice contiguous address space to 
> a Macintosh emulator like Readysoft's

I suspect it could.  Of course, ReadySoft's hostile port logic would have to
look for an MMU on a 32 bit system, and adjust accordingly.  And assume that
the Mac software isn't trying to access the MMU otherwise.  Since all the
Mac OS stuff runs in Supervisor mode, there's no way to trap MMU instructions
and add them to your MMU table.  Though far as I know, the MMU doesn't become
an issue with the Mac until you get to the 256K ROMs.

> 	-Ranjit

> "Trespassers w"   ranjit@eniac.seas.upenn.edu	mailrus!eecae!netnews!eniac!...
>   Giant SDI lasers burn 1,000 points of light in Willie Horton - Dave Barry
-- 
Dave Haynie  "The 32 Bit Guy"     Commodore-Amiga  "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: D-DAVE H     BIX: hazy
              Amiga -- It's not just a job, it's an obsession