Episode 4: WAPster Diving

This month, Paul performs Pascal programming and plays games, while Mike mines the WAP DVD and finds hidden treasure.  We discuss the latest MESS emulator developments as they apply to the Apple /// core, music and sound, driver and much more. Join us, won’t you?

3 thoughts on “Episode 4: WAPster Diving”

  1. With respect to the 6-bit DAC, it’s kind of like 1/4th of Amiga’s Paula or 1/32nd of the IIgs’ 5503: one sampled voice, but 6 bits instead of 8 and no volume control. You can play arbitrary sampled sounds on it.

    Where it gets annoying is that unlike those later machines it can’t feed itself new samples so the sample rate is simply how often the 6502 writes new samples to it. This requires either very carefully timed assembly code (similar to making tones by toggling the speaker) or using one of the VIA’s timers to interrupt at whatever sample rate you want.

    For a practical example of this sort of thing from roughly the same time period, the arcade games Joust and Defender used a sound board where a 6809 CPU synthesizes the sounds and outputs them to an 8-bit DAC.

    With respect to the floppy controller, I did credit Paul for the fixes in the official changelog so he’ll appear in 0.155’s messnew.txt 🙂 The changes have the Disk II and Disk /// emulation work with the floppies at the raw magnetic flux level, which should be useful for running protected originals (we should even be able to emulate “Catalyzing” protected /// programs eventually. Brrrrr) . Obviously the common .DSK and .PO/.DO dumps don’t go to anything like that level of detail so we reconstruct it on load and deconstruct it on save.

    In other work I emulated the Apple II mouse card and made it available on the ///, which involved hooking up interrupts to the slots (that doesn’t work quite the same way as on the II and may not be exactly correct yet). I can’t get it to actually work in Draw ON ///, but there’s an excellent chance I’m doing something dumb 🙂

    1. Thanks! Just realized we never wrote to thank you for the information on the DAC here, but this is interesting to know, I’d like to play around with this more. I haven’t had a chance to try the mouse port yet, but that’s very nifty. I’ve seen a couple of articles that talk about the differences between the II and /// mouse handling, though there’s probably nothing in there that will be news to you. I look forward to playing around with these, and if I see anything I can contribute notes on, I definitely will.

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