[Coco] CDi Emulator

[Joel Ewy]

Unless this CD-i emulator is pretty new, the only one I know of is not
open source, therefore not likely modifiable into something capable of
running MM/1 or TC-70 software.  Also, I believe that it doesn't really
emulate much of the underlying hardware, but rather intercepts the
CDRTOS (OS-9) system calls and library routines and translates them into
native OS (MS-Windows) calls.

I've given some thought to what would be a good starting place for real
MM/1 emulation, and I think the best bet would be to begin with
something like the Atari ST emulator ARANYM.  That emulator is complete
enough that it runs Linux/m68k and is used for building packages for
Debian m68k.  First, port OS-9 to that emulated Atari hardware.  [I once
tried booting Atari OS-9 disk images in ARANYM and couldn't get it to
work.  Bob Devries mentioned that OS-9 for the Atari actually made use
of the GEM or TOS ROMs for some of their hardware access.  So maybe I
wasn't using the right ROM images...]  Then replace sections of the
emulated Atari hardware with emulated MM/1 / TC-70 hardware by driver
module.  In fact, in most cases you wouldn't really even need to
eliminate the Atari hardware until your MM/1 part was developed and
tested.  No reason you can't have two different emulated floppy or SCSI
controllers in the same emulated computer.  This way you could have a
working system almost all the way through the development process.  The
Atari even has an MFP68901.  The MM/1 uses one of these on the CPU board
and another on the I/O board.  That and the processor give you a head start.

Once you had the emulator acting like an MM/1 it wouldn't be much more
work to emulate the rest of the hardware that would turn it into a CD-i
player.  The main problem would be finding documentation for the CD-i's
CD drive and controller interfaces.  OTOH, the modular nature of OS-9
means that you don't really have to emulate the underlying hardware if
you can produce OS-9 modules that provide the same functions and the
same API.  One of the complaints about CD-i was that they made you
access the hardware through proper OS and library calls rather than
banging directly on the chips.  It may have meant lower performance for
games, but it makes the job of the emulator writer much easier.

JCE

Dean Leiber wrote:
>
> On one of my searching missions for stuff for the archive, I came
> across a CD-I emulator. Since, a CD-i player is nothing more than a
> specialized OSK machine, I was wondering if anyone had tried to use
> one of these emulators as a generic OSK emulator? Any chance of
> turning one of these into a MM/1 or TC/70 emulator?
>
> Dean
>
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