Re: Universal Sound Board?

>I agree. When you want a DAC, buy a DAC. Though I think you can do
>multiplies quite a bit faster in a PIC than the 8051 (I've written math
>packages for both). So if you want to do any kind of, on the fly, volume
>control, sending the data through a PIC might get you a little better
>thorough put...

Hmmmm. We could do what the Universal Sound Board does and use PWM outputs
from the PIC tied to caps to make a envelope control for each voice
output...

Doesn't the 8051 have a MUL instruction? Thought for sure it did. Seems
like its a 24 clock execution time? (So yeah, if you run a PIC at 20MHz
and the 8051 at 12MHz, you'd have what-- around 48 instructions on the PIC
to do a multiply and come out ahead of the '51... That shouldn't be too
tough. ;-)

>I should start by saying Tempest *is* my favorite game, but none the less, I
>think the sounds of those Pokey chips basically *suck*.

Well, in practice I'd agree with you, but I think the old "beep-boop" and
weird grinding periodic noise sounds the POKEYs make are kinda cool in that
"retro" way. And 4 voices for $.80 (price of a Ball-Blazer cart) is hard
to beat...

>>Or if you're going to use serial anyway, just use a single PIC and one of
>>those Max528's. About $7 with serial input and 8 voltage output 8 bit
>>D/A's in one package...
>
>I like this idea a lot! I'll have to look into that Maxim(sp?) chip (Does
>Maxim make some cool chips or what?). I imagine the clock rate needed to
>constantly refresh 8 continuous samples of audio is pretty high. (Oh like:
>8*8*SampleRate)

I think it's more like 16*8*rate since there's going to be some bits to
select which channel to talk to. I think it's a 3-wire interface.

>It's also pretty simple to use an external latch (or two) as part of the
>addressing of the 68HC11 to allow for banking. And the 68HC11 being a nice,
>straight forward, Von Neuman device, table look ups [of the sampled wave in
>EPROM] is simple. Though for simpling data moving, it is a tad slower than
>tbe PICs...

Yeah, I always just OR the program and data store enable pins together on
the 8051... Aside from still having a "DPTR" it's a little more "normal"
to use that way... ;-)

>I know, hence the external counters and a lower end PIC. But then again how
>many sound cards do you intend to buy? Even if you used 4 $11 PICs, another
>$50 worth of "other stuff", a $50 PCB. Considering the prices I've paid for
>my collection of Sega Boards, a "Universal Sound card at $150" sounds like a
>deal to me! If one were available "right now", I'd be filling out a check,
>"right now"! And hell, if I owned the card I'd want the $25 reprogrammable
>PICs anyways! I'd want a "Universal" Universal Sound card!
>
>Am I the only one to pay more than $150 for a game board?

Well, there's those "magic" marketing price points.

(some lower ones) $99, $199, $249, $499, $999 (and the higher ones)

The rationale being that a particular group of consumers will be willing to
purchase a particular item since it's "under" a price that they consider
"high".

I'm probably overly price-aware since our "real" business is low-margin,
high volume. If we sell 250,000 or something a month and we're paying an
extra $.10 for it that's $300,000 a year off the bottom line. I definately
want the multi-game ROM/input mapper board to be $99 or under. If the
UniversalSB doesn't fit on there at that price I suppose it could be
another $99 board... ;-)

>Four 16 bit writes for the entire sound doesn't sound bad at all! The
>problem is that if the samples are not being fed through the CPU, no
>attack/decay control can be done.

Nightmare used a 4bit ADPCM sample system (Basically a telephone chip)
which they used a four bit mux to swap nibbles to the ADPCM on every
address clock. Kinda cool idea, pretty efficient, particularly compared to
having a processor fetch and store to the codec at the right rate...

>It's too much trouble anyway. That's what CPU's are for. What's the point
>in using a processor if it's just going to sit around and wait for the
>hardware to do what it should be doing itself? Those poor Atari guys just
>didn't have the luxury of cheap processors...

Well, yeah, they were just saving cycles for game logic I'd imagine
(Nightmare is pretty busy). I have a schematic from Atari for a "Sampled
Audio Cruncher" (never made it into a design as far as I know) that was a
68000 that mixed and played 8 bits samples out through a 12 bit DAC.
(Kind-of a souped up Bally/Midway Cheap Squeak Deluxe board.)

>PS I'll look around the local electronic surplus stores for the noise
>generator and let you know if I find anything.

Thanks, that'd be interesting.

Maybe we should be looking at modifying the existing Universal Sound Board?
It already has 9 DACs with Whit noise generators, etc. We could bank
switch the downloadable RAMs out with EPROM and add another couple
interface port latches and use the existing hardware card with a new
program to be the sound source for Zektor/Elim/SF...

-Clay

Clayton N. Cowgill Engineering Manager
_______________________________________________________________________
/\ Diamond Multimedia Systems, Inc. clay@supra.com
\/ Communications Division http://www.supra.com/
Received on Fri May 2 12:30:15 1997