Re: What's this AppleIIGS card?

[rubywand@aol.com (RUBYWAND)]

In article <22FEB199612030154@vax2.concordia.ca>,
spector@vax2.concordia.ca (Mitchell Spector) writes:

>
>	The Echo+ is also usable as a music and sound-effect board.
>Like the Mockingboard, it has a pair of General Instruments sound 
>chips (AY-8913).  ....
>
>	It works great with the large amount of speech-supporting
>software out there, but it doesn't seem usable as a Mockingboard
>replacement. Perhaps it has to do with the fact it uses the GI
>AY-8913 chip rather than the AY-8910? (Anyone know the differences
>between the two chips?). ....

    The only difference between the AY-3-8910 and the AY-3-8913 is that
the '8910 is a 40-pin IC with two 8-bit I/O ports whereas the '8913 is a
24-pin IC with no I/O ports. Evidently, Sweet Micro Systems used the '8910
for its MockingBoards because it was the only '89xx Programmable Sound
Generator IC available at the time the first MB's were designed. No MB
uses the '8910's I/O ports.

    If Echo uses the '8913 and, yet, is not MB compatible, the explanation
must be a difference in the way the two boards let the Apple II talk to
the PSG(s). MB's employ the 6522 peripheral interface IC to send data and
strobe the PSG command lines.

   



Rubywand