From: Aric.Caley@ofa123.fidonet.org
Newsgroups: comp.sys.amiga.hardware
Subject: Re: AA sound chip. Specs
X-Sender: newtout 0.02 Oct  1 1992
Date: 13 Oct 92  10:13:00

> Organization: Computer Centre, Monash University, Australia
> From: bull@vaxc.cc.monash.edu.au
> Message-ID: 1992Oct13.114522.90320@vaxc.cc.monash.edu.au
> Newsgroups: comp.sys.amiga.hardware
>
>        I'm not convinced that adding multiple DSPs is the best way to
> increase the number of audio voices. It's sort of like fitting entire

I dont think anyone is saying we need to add *multiple* DSP's.  One good
DSP will do quite nicely.

> extra engines to a car to tow heavy loads instead of replacing the
> current engine with a bigger one. I'm not saying "drop the DSP idea",
> I'm saying that we need to stop and think about what we're asking for.
>
>        If I'm not mistaken, DSPs normally have 2 or 4 channels.
> Adding another DSP just to get 2 or 4 extra voices is going to be an
> expensive exercise. I see a DSP as a number cruncher, highly suited
> for real-time audio and video processing, not simply as a "sound
> blaster card on a single chip". A more suitable approach would be
> to 1: improve Paula to raise the base level of functionality, and
> 2: add another Paula, or a Paula compatible, dedicated D/A chip
> on the DSP card. Paula compatibility/emulation keeps things clean for
> audio.device, and the ability to add a multi-voice sound chip to a
> DSP card gives A3000 owners an audio upgrade path (and A2000 owners
> if a Zorro2 version is released).

All we really need are 2 good, 16 bit D/A converters (stereo).  The DSP
can easily take multiple voices and combine them mathematicaly, and pump
it out the two D/A converters.  Right now, using something like OctaMED,
you can get 8 channels using this technique on any Amiga - it takes all
the power of a 68000 to do it.  It does 6 channels with higher quality on
a 68000 Amiga, and 8 with higher quality on an accelerated machine.  Now
think what a DSP could do.  You should be able to easily do 16 channels
at 16 bits with excelent quality.

I would like to see, for the lower end machines, an improved Paula.  I
would like to see Paula become a 32 bit chip like Lisa is.  With the 4
times bandwidth increase of Lisa (due to its 32 bit nature), we get lots
of new graphics modes - why shouldnt Paula also get a 4 times bandwidth
increase (and the blitter also for that matter)?  With 4 times the data
rate, you could do 16 channels instead of the 4 we have now, or you could
do 8 channels with 16 bit resolution.  That would be plenty sufficient for
low end / mid range Amigas.

On hi-end machines, the same Paula, but with the ability to feed that data
(the Audio DMA) into the DSP.  Actualy, I'd like to see a high-speed DMAC
just for the DSP.

It would also be nice to have some way of "multitasking" the DSP, so that
it wouldnt get locked up by one application.

Anyway, back to the original comment.  It seems very possible that a new
Audio.device could be written that used the DSP to give more apparent
channels.  Actualy, you could do it without the DSP, but it would slow
the CPU down a lot.

>           Bull@vaxc.cc.monash.edu.au  OR  bull@monu1.cc.monash.oz
>                    DOD# 251  '84 VF 750   Closet Ducatisto
>             Disclaimer. If you love your llama, let it lambada.


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Newsgroups: comp.sys.amiga.hardware