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Difficulties (Was: Nice demo, but why does it die?)
I'd like to point out here that although the NeXT does have a
68K and doesn't need to emulate the chip itself, as SoftPC does,
Executor needs to emulate the Mac Toolbox - all 5 volumes of Inside
Mac. This is where Executor is a much more difficult program to
engineer than SoftPC. On the Magic Sac emulator, you need to have
apple's ROMs, as you pointed out, and I believe you don't get to run
Amiga programs concurrently, as you do with Executor. There's a lot
of tricky code in those ROMs, which I think ARDI has done an
admirable job of reverse-enginnering.
I'll let Cliff be the final judge, but I'd bet that writing
the compatibility routines for the Mac was a lot harder than
reverse-engineering the PC BIOS.
Best,
Pete
pclark@bosslogic.com
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Sender: mspboss!bosslog!uunet!ictv.com!executor-request
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Date: Fri, 10 Apr 92 06:55 PDT
From: mspboss!bosslog!uunet!ruts.ccc.amdahl.com!kls30 (Kent L.
Shephard)
To: iclone!ctm@unmvax.cs.unm.edu,
ruts.ccc.amdahl.com!kls30@unmvax.cs.unm.edu
Subject: Re: Nice demo, but why does it die?
Cc: ictv.com!executor@unmvax.cs.unm.edu
THe one thing I'd like to say in response is that:
Liken and Quorum both have to emulate the processor, like SoftPC.
The NeXT
on the other hand has a 68K family processor. So instead of
emulating the
whole processor you grab the graphics and system calls. This is a
lot different
than SoftPC and the emulation of a PC on NeXT hardware. This is the
big reason
that SoftPC is slow. It not only has to emulate the processor but it
has to
intercept graphic calls to the bios and hardware. A much more
difficult job
than what's done in Executor. Liken is the same in that respect.
I would say that Executor is more in the same line of emulators for
the Mac that
run on the Amiga and Atari, that is same family of processors so
instruction
set mapping or emulation is not needed.
I understand that for the Atari and Amiga you need the ROMS, etc.
I'm not trying to take anything away from Executor, I think it's a
great
program. But I also think that SoftPC and Liken were more difficult
to write
just because you have the added difficulty of supporting the native
processor
that the stuff originally ran on through software.
I've written a software emulator for a vector processor for a PC.
This
included all registers and a couple of vectored interrupts. Ran
fine, but it
was a pain to support interrupts.
I hope you see my point.