• ### New Display Board

So it turns out I absolutely hate wiring diode arrays, and I would like to display all three registers, not just the input register and accumulator. (I was able to rework things to get it back down to three registers).

The seven segment LED display would require over 1000 diodes and I just don't care to do that.

So instead I've found a good deal on 24x IN-12B Nixie tubes and sockets and will use those instead. That eliminates the last few diodes and any semiconductors in the entire project.

In other news, I calculated that the core of the calculator, which can multiply two single digit numbers and then add another single digit number to the product, and then convert the binary result to BCD, will take 87 relays. It has a 34 relay latency that data has to propagate through. I measured the switching time of the relays I'm using in this part to be about 15ms, so it will take approximately half of a second for a signle digit calculation to take place.

This means that an addition or subtraction will take 4 seconds, a multiplication will take 4 seconds per multiplier digit (32 seconds for 8 digit x 8 digit) and a division, (which uses magnitude comparators, shifters, and counting subtraction) will take a maximum of 320 seconds (99999999/1) but will typically be much less.

• ### Minor tweaks

I just wired and tested one diode array used for decoding the 1 of 10 signal to the what the seven segment displays need. It took a long time.

The parallel multiplier was going to use diode arrays as well, but I am not keen on using 40 relays and 768 diodes. I looked into the double dabble algorithm and it actually seems pretty simple to do with eight +3 adding circuits with no output carry. Best guess is maybe 60-80 relays for a parallel multiplier and double dabbler, which will also cut down the amount of relays required in the adder.

I'm hoping to make at least 4 single digit additions or multiplications per second, which would allow for a complete 8 digit by 8 digit addition to be made in 2 seconds and a multiplication to be made in 32 seconds.

Also I think I may need four registers, not three.

And just like that, I have run out of relays.