Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cbmvax!daveh
From: daveh@cbmvax.commodore.com (Dave Haynie)
Newsgroups: comp.sys.amiga.emulations
Subject: Re: Emulator Mechanics
Message-ID: <19792@cbmvax.commodore.com>
Date: 12 Mar 91 22:39:53 GMT
References: <1991Mar7.093149.18707@mintaka.lcs.mit.edu> <19749@cbmvax.commodore.com> <1991Mar12.011418.24768@mintaka.lcs.mit.edu>
Reply-To: daveh@cbmvax.commodore.com (Dave Haynie)
Organization: Commodore, West Chester, PA
Lines: 36

In article <1991Mar12.011418.24768@mintaka.lcs.mit.edu> rjc@geech.ai.mit.edu (Ray Cromwell) writes:
>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? 

>>Without massive patching of the Mac ROM, I don't think so.  

>  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.

Well, the Mac OS fiddles with absolute memory locations, and the OS implements
function calls as line-A exceptions.  Apparently, all the absolute locations
are in low memory and get swapped as part of the process context when you run
Multifinder.

>I also wonder why readysoft used a special disformat for Mac disks
>instead of reading Amiga disks.

No doubt this was to make Mac software work on Amiga disks.  The Mac isn't
as nice about filesystem independence as the Amiga is, so you can't really
provide a loadable Mac filesystem kind of thing that maps Mac filespace
into Amiga filespace adequately.  So ReadySoft essentially just built a new
device driver, which uses Amiga-readable formats, but Mac filesystem 
organization.

This is apparently why Mac's don't generally talk to MS-DOS disks via an
alternate filesystem like CrossDOS or MSH, but instead use a user program for 
the conversion, along the lines of the old PC Utilities.  
-- 
Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests"
   {uunet|pyramid|rutgers}!cbmvax!daveh      PLINK: hazy     BIX: hazy
	"What works for me might work for you"	-Jimmy Buffett