Here’s the sound board used in Williams System 3 and System 4 pins from the late 70s to early 80s. It’s simpler than the System 6/7 board but similar architecture, 6802 CPU(similar to 6800) with 128 bytes of RAM, 2K ROM and a 6820 PIA driving a DAC. Curiously the ROMs for every game using this board seem to be identical so it seems they used the same sounds in all of the pins of this era. Maybe this shouldn’t be surprising since it’s right on the tail of the electromechanical chime era.
The top level file is set up for an Altera Cyclone II mini development board available on eBay for less than $20. There is a PS/2 interface to control the sounds which can easily be removed if you are going to attempt to use it in a real machine. This has not been tested in a real machine yet.
Here is the code, it’s a little messy but it will be cleaned up eventually if time permits:
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