1 Reply by david.given

(3 replies, posted in Other Platforms)

I'm building Apple 2 disk images for my CP/M-65 project. The crucial bit is shuffling the image into the right sector order because the bootloader uses this wretched soft sector remapping. I've got a tool here: https://github.com/davidgiven/cpm65/blo … shuffle.cc The right order is 02468ace13579bdf...

I wasn't aware that anyone had done softsynths for the Apple. I thought I was the first to do it on a 1MHz 6502 on the PET! I'd be interested to see how they work; I had a great deal of difficulty fitting 3.5 channels into the available CPU time, and that was with using a 6522's shift register to do much of the heavy lifting.

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2 Topic by david.given

(2 replies, posted in General Discussion)

I tried reverse engineering Tim Follin's Startip 2 music track and engine and porting it to the PET. It went... not great.

https://www.youtube.com/watch?v=B_SmzoQJBsQ

The issue is that the playback engine has got extremely ad-hoc timing. Every bit of it takes as long as it takes with no attempt to synchronise timings anywhere. So, depending on how much work it's doing, the pitch will change slightly. Because my new engine is using a different architecture, all the timings are different, and it's all fundamentally untunable. I suspect Follin simply did everything by ear. I've found transcriptions of this track, and the same note in different contexts will be represented by a different value in the data. To make it work I'm pretty sure I'm going to have to retranscribe the music from scratch, and, well, then it's not the same engine any more, so I'm going to leave it here.

Anyway, I thought people might be interested to see this.

Source: https://gist.github.com/davidgiven/ca16 … bef4504526
.prg: https://drive.google.com/file/d/1jRVbj3 … ?usp=drive

(I'd be interested to know what it sounds like on real hardware.)

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