Hardware emulation of a SN76489

Hey All,

This is fairly OT, but I think regulars here might appreciate this…

A couple of years ago I got really interested in emulating retro computers. In particular I build an FPGA emulation of a Microbee - an Australian home computer from the 80s. See FPGABee.

Anyway, back then you could get a synth module for it based on the SN87489 sound generator chip. So when I found an open source FPGA implementation of this chip I couldn’t resist hooking it up. I just used a simple 1-bit DAC which is not ideal, but it actually sounded pretty good.

Lemmings Recording from FPGABee

If you’re not familiar with FPGA’s, they’re fascinating technology - you design digital circuits on your computer in code and download them to the FPGA chip which “runs” the circuit. These circuits don’t need to be trivial either - my emulator includes a Z80 CPU, RAM, ROM, video controller, keyboard decoder, disk controller, the sound chip etc… and still has plenty of room.

Speaking of emulators, I also wrote a C# emulation of a Microbee - and it was that project that planted the idea of moving Cantabile to C#.

Fun stuff - though very time consuming.

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l loved the recording, who wouldn’t smile after hearing that! :smile: I used to create custom Motorola 6802 industrial testing devices for the factories near where I live. Also time consuming to program. Very cool Article Brad.

Thank You

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Thanks Dave.

There’s something very appealing about these old devices - I think it’s just that they’re simple enough to understand from top to bottom.