Hello together / Hallo zusammen,
Some explanation about the "inconsistency problem":
Yes, the resistor interface between C64 and Unicart64 was finetuned on my machines.
It seems to be perfectly working on many C64 machines, including my 2 C64 boards, but on some machines it crashes and leads into "inconsistency" behavior.
The root cause is the dropping main 5V voltage on some C64 machines "too much down" (e.g. 4.6V, 4.5 V ...). It corresponds also with the previous FunFun's observation replacing older SID chips and measuring main C64 voltage.
I have not counted with such bigger voltage dropping down, so I have finetuned other new values of resistors to be able to "move down" voltage window and accept lower values from C64 side.
So, Ruben (Chiemsee), thank you very much also to you for your testing and helping to observe true root cause of such inconsistency !!!
Because of restricted free time I will not respond fast, but I'm still here ...
Greetings to all true C64 fans !