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catmeows wrote:Hello. I wonder what kind of synthesis is used in following three ZX games. Maybe someone here could guess it by ear ?
2) Antiriad - https://www.youtube.com/watch?v=0gtbIY8sAE4
I guess this is single square wave appergio ???
It's not. Antiriad uses two channel square with 8 bit counters but they are played for very short time (is that called staccato ?) with distinct interruption. It is clearly hearable when you change global tempo variable.
I also peeked into Topo Soft's engine (for example Titanic) - it is single channel with two oscillators combined by xor.
utz wrote: Also I wonder if it's always the same engine or if there's some evolution from Cybernoid -> Cybernoid II -> Netherworld/Stormlord.
Cybernoid 2 and Stormlord seems identical, including register allocation, at least in core.
Cybernoid 1 is something completely different from Cybernoid 2 and Stormlord.
Netherworld is very similar to Cybernoid 2/Stormlord, including register allocation in core, but I see little differencies regarding instructions used in loop management - just the tail of core, first part of core is identical. So perhaps it was Cybernoid 1 -> Cybernoid 2 + Stormlord -> NetherEarth ?
I had finally time to look inside. Stormlord is 2 channel appergio. The time single note is playing is indepedent on interrupt but in song it is roughly aligned to 1/50 of second.
Note generator can either rest running dry loop without switching 5th bit of port 254 or can generate note. Now it is quite interesting. There is square wave generator and each note is enconded as pair of 16 bit frequency and 8 bit duty modifier. The duty is ON for time (frequency + modifier) and is OFF for time (frequency - modifier).
What a piece of software archeology 
Thank you.
Hello. I wonder what kind of synthesis is used in following three ZX games. Maybe someone here could guess it by ear ?
1) Stormlord - https://www.youtube.com/watch?v=ygE5HOFr5FI&t=84s (start of video)
2) Antiriad - https://www.youtube.com/watch?v=0gtbIY8sAE4
I guess this is single square wave appergio ???
3) Super Dragon Slayer - https://www.youtube.com/watch?v=4Iztvbo09rU
Thanks if you answer and sorry for bothering if you are not interested.
Catmeows
Posts found: 6