Sorry, not trying to be arrogant. I know the designers of the original Mockingboard (sound card for the Apple //) were actual engineers and I'm a hobbyist at best.

So I had a crazy idea. The original Mockingboard had two VIA's and two AY-3-8912's (or '13). Since the AY needs an 8-bit I/O bus and a few control pins, they tied one AY to one VIA.

VIA1 would use port A for the data and port B for the control lines (BC1, BDIR, etc.).

My idea was to try and use THREE AY's with TWO VIA's.

VIA1 Port A <-> AY1 Data
VIA1 Port B <-> AY2 Data
VIA2 Port A <-> AY3 Data
VIA2 Port B <-> Control pins for AY1-3.

You only really need two control pins for an AY. BDIR and BC1. So that would be six pins.

Anyway, just wondering why they didn't design it that way? I suspect one reason was cost. Another AY chip dipped into their bottom line. Also, you could buy the Mockingboard with only one VIA/AY and then populate it with TWO later. Might be more difficult to do this with three.

Once I get my SBC running, this is something I want to try and see if it works.
It will be a little more difficult to control them but it shouldn't be too bad. Just masking Port B on VIA 2 for whichever AY you want to work with.

Thoughts?

_________________
Cat; the other white meat.

If one is good and two are better, are three actually better yet? Or are we getting diminishing returns on our investment here, and just complicating our interface? I'm not trying to sound like a jerk ... I honestly don't know the answers to those questions.

Mike B.

It might be worth noting that the price of a product in the shops goes up by four times the price of an extra component: removing a chip, or a socket, can make quite a difference, especially if the product is aimed at a particular price point. In this case, the target price point was $99 - so that's $25 build cost, conventionally.

Probably more importantly: two chips meant the board offered stereo, presumably that would be attractive compared to a mono board. But adding a third chip doesn't add a feature, it just bumps up the number of voices. But a very keen customer can (it seems) buy and install two boards - that's a feature, the ability to have two boards. So with a single low-cost product, you can sell a few more.

Well, a few games (Ultima 5) actually supported two Mockingboard cards. That would be four AY's. However, they only used three of them. So there was certainly a need for more than two. Especially when you look at the Phasor card (four AY's on one card IIRC) and the music construction kit.




I didn't know that about the price. But it confirms my suspicion that cost was probably the primary reason.



I can't remember if the original board offered stereo. The later ones might have.

_________________
Cat; the other white meat.

"I bought a Stereo! Wow! With two speakers!
But then I heard the quadraphonic with the four speakers and I was like this is it, so I got rid of the stereo and got the quad.
I'm listening to this thing and I'm like 'Hey this sounds like s**t!'
So, I got rid of that and got the dodecaphonic with the 12 speakers.
This was more to my liking ... for a while. But the gear gets pretty sophisticated pretty fast and I got rid of that and got the milliphonic with the 1,000 speakers.
And I'm listening to that one and I'm like, 'Hey, this sounds like s**t too! The other one was s**t one, this one is s**t too!'
So, I traded that in and got the googolphonic, which is the highest number of speakers you can have before infinity.
Sounds like s**t!
So, then I said, 'Hey, maybe it's the needle!'
I had the typical diamond needle. I searched around got the moonrock needle, cost me 3 million bucks, but what the hey. So, now I have a googolphonic stereo with a moonrock needle.

... Sounds like s**t."

-- Steve Martin, 1979.

Don't get me wrong, Steve Martin is one of the best comedic geniuses ever born...but wouldn't milliphonic mean 1000th of one speaker? Did he not mean kilophonic?


LMAO

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Cat; the other white meat.

Milli was defined as 1/1000th in the metric system, but it comes from Latin 'mille' where it means 1000 (and still does in Italian). And it keeps its original meaning here and there, for example in 'millipede' (or 'milliped' for some of you) which is probably what inspired the word 'milliphonic'. Milli probably sounded more familiar than kilo to Americans at the time I guess.
Anyway, Steve Martin can play the banjo at the speed of light, or nearly..

I think it is easier:

Put all of the data lines on the same port (a), and You've got PortB control line support for up to 4 AYs

The answer to your question was in your note. They were Engineers. An Engineer designs an elegant solution. 2 VIAs for 2 AYs is elegant, and easy to program. Set the base address of the voice you want, and you're there.

One can argue that the 1 VIA -> 2 AYs is also elegant, and that's left as an exercise. But, it is not as elegant, as you note, from the SW side.

Jim

Once again, I learn something from this forum. Why didn't I think of that? :-/

I see what you're saying too about it being elegant. I would think that the "Woz" way would be to use one VIA for four AY's. Or, knowing Woz, 8 AY's with one VIA that I can't fathom. LOL

Hmm...I will have to try the multiple AY's on one VIA and see how I like the programming.



**EDIT**

Actually, hang on....how would that work for four AY's? IIRC, you need a way to address the AY individually. How would you disable three of them so that the data bus wouldn't affect the others from playing the new command?

Hmmm

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Cat; the other white meat.

Remember that the AY only looks at the bus when the 2 control signals tell it to. By holding them low or high or whatever, you effectively allow it to ignore the bus.

Jim