Audio

Audio Hardware

From: Joel Ewy
Date: 1/25/2007
Subject: Re: [Coco] CC-Five (was Re: Pseudo CoCo4???) (LONG)

A couple questions come to mind here:

1.  Does the CoCo care what kind of microcontroller is in the S/S Pak as
long as it does its job in the expected manner?  I wonder if one could
sub a PIC core (or maybe a 68-something) and then also make it a more
general-purpose I/O processor.  It could help out with faking a floppy
controller and who knows what other kinds of things.  One thing that
shouldn't be emulated is the S/S Pak's failure to run at 2MHz (and above!).
2.  How hard would it be to combine the Orch-90CC and the Speech/Sound
Pak?  I'm not real clear on how the S/S Pak is set up, or where the
dividing line is between analog and digital on it.  But surely an
amplifier is common to both, though the S/S Pak is perhaps just mono? 
Putting a stereo amp in the external hardware would just make sense. 
Now if the AY3-8913 produces a digital output, that can just be buffered
in one or both channels of the Orch-90, then out to the DAC in the
external hardware.  Otherwise, just add an analog mux in front of the
amp.  I don't know what addresses the S/S Pak uses, or what kind of
space might be left in its register mappings.  Might have to have some
virtual Multi-Pak action going on there.  Might have to improve the
address decode sections and provide a way to select which source has the
audio out bus.  That might require a one-liner to poke a register before
running a program, or a (virtual?) toggle switch for use with ROM Paks. 
But ideally one could make these things both work, so the CC-Five (or
whatever), could run just about any existing CoCo program that uses
sound hardware, whether synthesized or sampled.

JCE

Mark McDougall wrote:
> > jdaggett@gate.net wrote:
> >   
>> >> Now the Speech/Sound card module is a different critter. Unlike the
>> >> Orchestrra 90 card, which the main micro runs code from, the
>> >> speech/sound card has its own dedicated processor,  TMS7040. Along
>> >> with that is its own ram. The heart of the sound is the AY3-8913
>> >> sound chip, and the SP0256-ALS speech chip. I do believe there is a
>> >> HDL version of the sound chip available that maybe open source. The
>> >> speech chip may still be floating around in surplus markets.
>> >>     
> >
> > My colleague here has implemented the AY-3-8910 for our PACE project. It
> > was reasonably trivial, if not a little resource-hungry. I understand
> > that the 8913 is basically just 3x 8910 cores in one chip?!?
> >
> > I'd suspect that the SP0256-ALS isn't very difficult to emulate - AFAIK
> > those speech chips where just wave tables...
> >
> >   
>> >> The TI micro is a 4 bit micro that is now obsolete. That along with
>> >> the sppech chip would be the hardest to reproduce. SO that kind of
>> >> forces backward compatiblilty with the current cards.
>> >>     
> >
> > That's a different kettle of fish, but still within the realm of
> > possibility, I think. I'd love to do my own cut of a processor, for
> > example, and maybe this 4-bit micro is a good candidate???  :) 
> >
> > Regards,
> > Mark
> >
> >   

From: Joel Ewy
Date: 1/26/2007
Subject: Re: [Coco] CoCo 4 (or 5) perspectives: close hardware emulation?

Frank Swygert wrote:
...
> Legacy support is a must, but is there a need to support the Pseech/Sound pak AND the Orchestra 90? Which was most often used? I ouldn't worry about future support -- an enhanced sound capability could be an added feature of the "new" machine. 
> > ...
> >   
Well, judging from the schematic, the Orch-90 hardware should be nearly
trivial to implement, and at least some portions of it could be shared
with that of the S/S Pak.  (Audio amp, address decode logic, ROM,
probably even DACs.)  I think that the S/S Pak would be the more
interesting capability to provide (interesting from the perspective of
arcane and fascinating, but possibly also in terms of providing support
for existing software), but since the Orch-90 hardware is so blitzin'
simple, I don't think it would cost much to include it as well.  And
arguably it is more useful in these days where sound on computers is
mostly a matter of playing back digitized samples.  It might be a little
bit of a challenge to integrate them seamlessly together in the way I
have in mind.  I'm not sure.  If the S/S Pak is too difficult to
emulate, then the Orch-90 by itself is the logical choice.  But if the
S/S Pak can be done, why not throw the Orch-90 in as a bonus.  Assuming
the 6-bit DAC is still in, such a CoCo would be able to support just
about any existing CoCo program that can produce a sound.  And having
good built-in sound hardware would surely be an enticement to future
programmers.  One of the problems with the CoCo was always that all the
good hardware was optional, and relatively few people bought it, so
relatively few programs took advantage of it.

JCE