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From: rjc@geech.ai.mit.edu (Ray Cromwell)
Newsgroups: comp.sys.amiga.emulations
Subject: Re: Emulator Mechanics
Message-ID: <1991Mar12.011418.24768@mintaka.lcs.mit.edu>
Date: 12 Mar 91 01:14:18 GMT
References: <1991Mar7.093149.18707@mintaka.lcs.mit.edu> <19749@cbmvax.commodore.com>
Sender: daemon@mintaka.lcs.mit.edu (Lucifer Maleficius)
Organization: The Internet
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In article <19749@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes:
>In article <1991Mar7.093149.18707@mintaka.lcs.mit.edu> rjc@geech.ai.mit.edu (Ray Cromwell) writes:
>
>> Why doesn't AMAX multitask? It should be EASY to run multiple copies
>>of the Mac ROM as a task (since its a rom, its mostly pure code, except
>>each task would need to alter where the ROM things the system memory is.)
>
>Without massive patching of the Mac ROM, I don't think so.  The same reason
>you don't have more sophisticated multitasking on the Mac itself.  You can't
>run multiple copies of the same Mac ROM code, since the code is not reentrant
>like Amiga code.  Without some clever MMU tricks, I don't think you could 
>easily relocate things such that several different copies of the ROM code
>could coexist.  At least, you would expect Apple to have considered any of
>the more mundane tricks available on any 680x0 system.  Apple does seem to have]
>decent technical folks, I doubt they missed any easy tricks...
>
>Via MMU, you could certainly get further.  Multifinder didn't do that, since
>it would have required an MMU based system for any multitasking.  I'm surprised
>Apple didn't work out anything like that for their MacOS-under-UNIX, though.

  Well  it's not a heavy loss if you can't make the Mac ROM resident, but
why does AMAX have to take over the Amiga's operating system? The only
thing that would make it really diffcult to run MacOS under
AmigaDOS is if Mac code fiddles with absolute memory locations or the
OS implements function calls as traps/interupts.
I also wonder why readysoft used a special disformat for Mac disks
instead of reading Amiga disks.