[Coco] CDi Emulator

[Joel Ewy]

Allen Huffman wrote:
> On Apr 21, 2008, at 6:36 PM, John W. Linville wrote:
>> As I understand it, the MM/1 chipset is basically the same as what
>> is in some of the CD-i players.
>
>
> They are at least using the same CPU and video chip. I know when Boisy
> first showed off the CD-i OS-9 shell at an AtlantaFest, we were pretty
> excited about the idea of an add-on keyboard setup to let us turn
> cheap consumer CD-i players in to OSK machines, though that was a task
> larger than our resources.
>
The MM/1 and TC-70 use the Signetics 68070 processor, which is in some
early CD-i players.  They also use the Signetics SCC66470 Video/System
Controller (VSC) which was also developed for and used in some early
CD-i players.  However, the CD-i players that used the 66470 actually
used two of them in tandem to achieve higher bit-depths for the video. 
Consequently, while the MM/1 and the TC-70 have only 8-bit video, CD-i
players can do 16-bit video.  Later CD-i players, like my
(comparatively) cheap Magnavox used a more highly integrated version of
the VSC in a single chip.  This is why the MM/1 and TC-70 really have
little hope of running most CD-i software titles.  But a CD-i emulator
that really emulated the hardware wouldn't take much more work to be
able to run MM/1 or TC-70 software.  And while an MM/1 emulator that
only emulated the single 66470 wouldn't cut it for CD-i, it would be 90%
of the way there.  Adding the extra hardware in emulation is quite a
different matter from wedging another VSC onto a physical MM/1!
> I'd like an MM/1 emulator.  I have much more attachment to my CoCo and
> would like to keep the hardware around, but not so much with the
> physical MM/1.
>
Well, if you do decide to chuck the MM/1, you could always chuck it in
my direction!  :-)

JCE
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