They’re nowhere near as complicated as the 1 bit ALU boards, but they do contain the accumulator circuit as discussed in our “Introduction to Digital Computers Part 4 video, along with a single tristate circuit for allowing the contents to be written to our bus, as discussed elsewhere in the same video.
These accumulator circuits are used as-is with the accumulator of our transistor-based circuit, and with additional circuitry for our flags register.
Of course this will take a while to build–and I have another 1,000 transistors and resistors on order (because ordering in bulk is cheap)–so hopefully I will be able to demonstrate a working accumulator with the ALU circuit built earlier.
Fortunately the boards (which implement the logic for a 1 bit accumulator) are not quite as complicated.
This is starting to get exciting, because instead of just showing addition we can show state, that is, we can show intermediate results being stored away and used for subsequent operations.
The Hacking Den 