September 4th, 2024

Mockingboard 4c+: Because Interrupts Are Hard

The Mockingboard 4c+ enhances audio for the Apple II //c Plus by providing interrupts, using Yamaha AY-3-8910 chips, addressing historical limitations in sound support for Apple II games.

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Mockingboard 4c+: Because Interrupts Are Hard

The article discusses the Mockingboard 4c+, a sound card designed for the Apple II series, particularly the //c Plus model. It highlights the challenges of audio processing on the Apple II, which lacks interrupts, making it difficult to manage sound alongside other game functions. The author explains the historical context of game loops and vertical blanking, emphasizing how sound and video processing share similar challenges. The Mockingboard 4c+ addresses these issues by providing interrupts, allowing for more sophisticated audio playback without disrupting the main game loop. The board features original Yamaha AY-3-8910 sound chips, ensuring authentic sound quality. The article also touches on the historical lack of support for sound cards in Apple II games due to a cycle of low demand and limited software compatibility. The Mockingboard 4c+ represents a modern solution to these historical limitations, enabling enhanced audio experiences for users of the Apple II //c Plus.

- The Mockingboard 4c+ enhances audio capabilities for the Apple II //c Plus by providing interrupts.

- The Apple II's lack of interrupts complicates audio processing, making it difficult to play sound during gameplay.

- The board uses original Yamaha AY-3-8910 sound chips for authentic audio quality.

- Historical support for sound cards in Apple II games was limited, affecting their popularity.

- The Mockingboard 4c+ is a modern solution that allows for improved sound integration in vintage Apple II systems.

Link Icon 3 comments
By @apricot - 6 months
I remember one action game on the Apple II that played music during gameplay: Microwave. But the sound was made on purpose to sound kind of choppy (a bit like voice fry), so that there was some leeway to fit graphics updates and calculations. I never disassembled it but I can imagine the pain it must have been to keep the game loop close to constant time.
By @egypturnash - 6 months
By @deater - 6 months
it's interesting the 4c+ has a Yamaha variant of the chip, probably for the best.

Recent other Mockingboard replicas use AY-3-8193 which turn out to sound awful, especially when trying to play ZX-style chiptune/demoscene music