At the moment I am working on the system memory...based on an arduino board (because it would not be very funny to build a system memory based on relays or diodes, it would be boring, expensive and would need a lot of space).

Here I am testing the memory software for the arduino (which is the core of the system memory):

The following board is a voltage divider for the data bus and the adress bus...the relay-CPU is working with 24V, the arduino ist working with 5V.