Apple II Mockingboard Code


The Mockingboard, introduced around 1981, was a sound card for the Apple II series of computers. It has dual AY-3-8910 chips on it, providing a total of 6 channels of square-wave sound, plus noise and envelope effects.

It was only used by a smallish subset of contemporary games, but it can be fun to play with when doing retro-coding.

You should also see my Raspberry Pi-Chiptune player page; I developed that board (which is essentially a Mockingboard for the Raspberry Pi) while waiting to buy one for my Apple II.


The Kerbal Space Program theme. In case you are curious the "game" sequence tacked on the end is from my BASIC version that you can find here (sadly it currently only has a 1-bit speaker rendition of the song)

You can see more of my projects that use the Mockingboard on my Apple2 pages.


My Apple II setup. In this picture it's playing the Pure Noise Demo by French Touch which is more impressive than any of the stuff I've written myself.


Apple II Code/Disk Images

Development Log

4 September 2018
Fix bugs in interrupt code where we weren't restoring A right on older Apple II models.

9 February 2018
Finally got the 6-channel support going. Two problems that took forever to find; an extraneous $ in a constant (making it hex) and also forgot to initialize Y to 0 in two spots.

8 February 2018
Working on 6-channel support. Should just be cut-and-paste but the two chips play out of synch, trying to figure out why.

7 February 2018
Interrupt based playing working! Also moving over some images from the demo, have to compress them so everything fits in the 20kB between the high-res page and DOS.

5 February 2018
Have a bare-bones compression of the files going so they can actually fit in RAM. Not really good enough for real chiptune files, will have to use LZSS or something for that.

4 February 2018
Have some music playing! I am converting .ym5 files using a hand-built tool.

3 February 2018
Got my Mockingboard in the mail and dug out the 6522 and AY-3-8910 datasheets to see if I can get something playing on it.

Other Apple2 Projects
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