Yes, the serial buffer is included in the motherboard. The problem is not so much for OUT but for IN, if the buffer fills up.
As for the bus addresses, the counter program starts from the lowest address. The mainboard obviously knows how much RAM is present and performs a translation to the first available low address. Nothing transcendental.
I did not understand the connection with VonNeumann architectures, this is a classic vonneumann architecture, only that the information is in base 3...
Anyway you seem to be really very expert, certainly more than me (I am mainly a programmer and I had to learn these things at low level practically by myself), you could actively help the project...
As for the bus addresses, the counter program starts from the lowest address. The mainboard obviously knows how much RAM is present and performs a translation to the first available low address. Nothing transcendental.
I did not understand the connection with VonNeumann architectures, this is a classic vonneumann architecture, only that the information is in base 3...
Anyway you seem to be really very expert, certainly more than me (I am mainly a programmer and I had to learn these things at low level practically by myself), you could actively help the project...