I know there is some CIC defeat cicrcuits wich sends nasty negative voltage spikes into the console's CIC, that those were bad, and that now it's possible to have a MCU imiting the CIC definitely and unlocking it just as if it was a real one.
But I still have a idea for cheap CIC defeating, that shouldn't harm the console if used correctly.
Since the cartridge and the expansion port have direct acess with the 4MHz clock, I don't exactly know how the oscillator is made, but I guess it would be possible to make a circuit that fools the oscillator and prevent it from oscillating at all, making the CIC in the console not being clocked at all and just stay in it's powerup state. I guess this could be done by overloading the CIC clock line capacitively. An exact shematic would require the oscillator circuit, so that it's possible to tell how to make it not oscillate any longer.
But I still have a idea for cheap CIC defeating, that shouldn't harm the console if used correctly.
Since the cartridge and the expansion port have direct acess with the 4MHz clock, I don't exactly know how the oscillator is made, but I guess it would be possible to make a circuit that fools the oscillator and prevent it from oscillating at all, making the CIC in the console not being clocked at all and just stay in it's powerup state. I guess this could be done by overloading the CIC clock line capacitively. An exact shematic would require the oscillator circuit, so that it's possible to tell how to make it not oscillate any longer.