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There is also BKBTL that has a Qt port and is supposedly works under Linux.

To be honest, I have no idea what the BIN format is, and where it comes from.

177716 has a lot of other stuff, ranging from tape controls to CPU reset vector (!). Don't forget, it is a 16-bit register with plenty a bits on a really oldschool architecture.

Here is a list of emulators for Windows. The list says there are better options, but I prefer to stick to one I'm most familiar with, Bashkiria-2M emulator (called just Emu).

So far I have found about 5 beeper editors, but was able to load and hear something from with only one, with a 3-channel engine, called Klavesin (attached).

How to get it started:

Start Emu
Select BK-0010_01
File/Open, set filter to all, select klaves.bin

All others are disk based ones, so you have to be a bit familiar with the MK-DOS on BK-0011, which looks much like Norton Commander from DOS era. Then it gets worse, as neither of the editors have a demo song loaded (but there are some on disks), it is all in Russian, and it considers you know something about the thing. So I wasn't able to figure out any of those yet. Seen that one has loadable 2-ch and 4-ch drivers and a few songs ripped from ZX Spectrum (judging by the filenames).

If you'll go the Nth/note with time signatures route, it will be not possible to properly support in tracker-alike editors (I had to replace such formats in some classic engines in 1tracker). Many also consider this format to be difficult to write by hand. So while it may have its own benefits, it dooms the format to never gain popularity.

Thanks to utz's input I got PET running in MAME. Turned out that MAME emulates 6522 quirks better, like, VICE would allow incorrect code to work just fine. However, MAME's SR produced pitch is twice higher than it should be.

I'm working with VICE, as I wasn't able to set up MAME properly. Judging by MAME source code, it does emulate IRQ on shifting, or trying to do so, at least. Latest updates to 6522 emulation there were doing in August, so it is kinda alive.

Emulation quality in VICE, on the other hand, is kinda questionable. It is incomplete, and the way the sound emulated is really weird. Like, direct CB2 control sounds unfiltered, while SR-driven sound is clearly filtered with very weird curve, it gets quieter as the pitch rises, up to the point of being really faint, then gets back to normal volume. So it sounds like a mess in a normal music. Also pitch and frame rate seem to be a bit off.

I didn't find any in-depth docs other than that you're mentioned, and I missed pet-io-2.txt altogether (thanks!). I also used 6522 datasheets, there is three of them, and they're actually different. Synertek SY6522 from 1982 (not 1978!) seem to be more detailed in the timers section. I also looked up VICE and MAME source code.

As I don't have access to the real thing, and active back-and-forth is kinda difficult to do (David is busy man), I can't say for sure. However, Synertek datasheet mentions it explicitly - first enable shifting, then load value to the register to start shifting. As for bit 5 of ACR and loading $ff, I did it other way, by toggling bit 5 of PCR - it does work on the HW regardless of the shift register contents. However, there is the missing notes issue, may be related to either of these things. Will try your approach (looks more elegant), thank for hints.

T2 high byte is not supposed to work in the free running mode. I hoped there is some hack to make it work, but considering not so precise emulation and lack of real hardware (not even sole 6522 chip) on my end, I can't do tests. Well, the main issue with pushing PET is that it isn't emulated well (not all timer modes covered, for one), and there is like 1.5 PET emulators around (.5 in MAME, difficult to setup).

To me it seem the only viable way at the moment is to use IRQ to toggle CB2, I did it as a software Shift Register imitation there. However, there is some issue on the real HW that is not figured out yet is that some tones disappear when you switching between IRQ and Shift Register (just on the transition point, maybe IRQs get skipped?), and this behavior is not emulated (works just fine in emulator).

Another issues are that default IRQ handler pushes all the registers before going IRQ trampoline, which wastes a ton of time; default system handler still need to be called once a frame (to make keyboard input work for the game), which introduces clicks; and unexpectedly annoying one, speaker in PET barely can reproduce low frequencies, they're getting very quiet.

I don't think I did anything that would break this compatibility. It is an SDL2 app, maybe something happened with the lib in lastest updates. Will check it out sometime later, thanks for report.

Thanks for report. Turned out there is a metric ton of various issues in the v0.3 release, working on fixing them for a while now.

That's nice, please remind me if there are major issues with tracker or engines, maybe I'll get another round of updates to fix (some of) them.

Relistened it again. Damn, such a great song and sound.

I recall I didn't recognize my own engine here when I heard it for first time. Yet another example that you never really realize true limits of your creation(s). Happened with Tritone and Octode engines in the past as well, even though I was able to recognize them, but was surprised by what composer guys managed to pull out of those.

Sure, but this is done on per-engine basis, so no quick fix. Some engines do break long lines, while others (Tritone Digi?) not. Will handle this a bit later.

A ton of distractions happened since, but English translation of the making of the demo is finally here: https://habr.com/ru/post/486010/