@pmprog,
thank you so much for that detailed descrpition. Especiall at the important technical part, concerning the play routines, I see now much clearer. But might be, I can get the oppinion of some others, as well.

@others:
Is there a way to patch the sid-file from the goattacker to make it play on the MEAG65 in C65 mode?
According to my assumptions only few bytes concering some register adresses and something concerning the timer would have to be patched.
I allready have the corresponding workflow to patch a sid-file to run on the C128 in C128 mode, and my first idea was to learn from that, but the person that started that couldn't finish it...so I do no see the compleete way.