ranjit@eniac.seas.upenn.edu (Ranjit Bhatnagar) (01/26/89)
I was wondering - does the MMU in the 2620 do address remapping, or just protection? If the former, could it be used to give a nice contiguous address space to a Macintosh emulator like Readysoft's - thus allowing the mac emulator to coexist with Amiga tasks? (I assume that the main reason it currently doesn't is that the Mac plays with low memory, needs contiguous memory, etc.) (By the way, has anyone who got on Readysoft's mailing list about the emulator actually received anything?) -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
daveh@cbmvax.UUCP (Dave Haynie) (01/27/89)
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
ditto@cbmvax.UUCP (Michael "Ford" Ditto) (01/27/89)
In article <5819@cbmvax.UUCP> daveh@cbmvax.UUCP (Dave Haynie) writes: >Since all the >Mac OS stuff runs in Supervisor mode, there's no way to trap MMU instructions Sure there is, that's what all the 68020 virtual machine support is for. It's for that very reason that the mov sr,ea was made a privileged instruction, so that you could run OSes in user mode without their knowing it. It would cause a slight performance decrease, since every privileged instruction in the Mac OS would have to be emulated. -- -=] Ford [=- "The number of Unix installations (In Real Life: Mike Ditto) has grown to 10, with more expected." ford@kenobi.cts.com - The Unix Programmer's Manual, ...!sdcsvax!crash!elgar!ford 2nd Edition, June, 1972. ditto@cbmvax.commodore.com