ALU Chip not loading

[Greemngreek]

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[xedover]

I suggest drawing a really big box, labeled "ALU" with all the input and output wires.

Then inside that box, start drawing your internal parts and connecting those wires to each other.

The first problem I see is that you got an output wire, "out", connected to an input wire "Or16Way(in=out...", "Or16(...b=out..."

You can't do that.

Then you have a wire, "drop", that's not connected to anything at all.

[xedover]

also...
you may need to use the trick in Survival Guide to create multiple sub-bus variables to be used later:
https://www.nand2tetris.org/hdl-survival-guide

[Greemngreek]

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[xedover]

sure, but if you'll notice... they don't have any output wires connected to inputs.

instead, they create a wire named "oo" that is the output of one part, and they use it as input to another part.

edit: I should say "they don't have the main output wire connected to inputs"

[Greemngreek]

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[xedover]

I can't say for sure... but seems unnecessary and out of place to me

[Greemngreek]

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[WBahn]

My guess is it's just there to make it clear that they didn't forget the signal, just aren't using it.

Pros and cons. What if you have multiple such signals? High risk of accidentally connecting them together.

I'd recommend leaving unused outputs unconnected as long as the tool allows it.

On the other hand, NEVER leave unused inputs unconnected, even if (as is the case more times that I would like) the tool does does allow it and does what you would like it to do in response -- the real world isn't nearly so forgiving.