Stuck on OR gate.

[John]

I feel rediculous.
Like I feel I've always utilized the "art" side of my brain more than the "logical" side.
But this is almost demotivating for me.

I've spent the last hour or so trying to figure out the OR gate on a whiteboard.

But I'm absolutely determined to complete this game without looking up the answers.

Is there some sort of strategy for trying to figure out logical flows?
Because the guess and check strategy I'm utilizing does not at all seem efficient.

[icy]

There are step-by-step instructions/algorithms to create any kind of gate, but I can't really recommend using them for the game, as you don't really gain a sense of achievement in my opinion by just following a list of steps (reference: https://en.wikipedia.org/wiki/Karnaugh_map).

What I recommend you to do is to think about similarities to stuff you already build and/or break down the problems.

At the example of the OR gate, first try to understand/rephrase what it is doing in order to see connections to what you already know or to gates you already build (mild spoilers ahead):
- It outputs 0 if both inputs are 0
- If you think about it, you already have a gate which is very similiar
- That gate is the NAND gate... as it only outputs 0 if both inputs are 1
- Can you use any of your already completed gates to make the connection?... (no further spoilers)

The puzzle progression is roughly in a way, where 80% of the solution is reapplying what you already know and 20% of the solution is "connecting the dots" so to speak...

[Jack Draak]

For about the first weeek or so that I was trying to wrap my head around Boolean Algebra and logic circuits I was having a heck of a time, myself. Then at some point, something clicked. I was able to start pumping-out circuit diagrams (for the fairly simple chips) often having them pass on the first go.

I'm positive that one major helper was drawing my circuits. I did a lot of that. I'm still doing it. As an artist, this part should come easy for you :)

The next big helpers were when I started to understand the meaning (and usefulness) of truth tables, K-maps, and other Boolean rules.

I wasnt able to do some obvious optimizations that were hidden to me, until after I took the time to draft a circuit entirely with NAND gates, then walk from gate to gate, figuring out what each wire state would be with any given input(s).

I'm also doing "From NAND2Tetris", and have completed all the chips for the first 3 sections... It was a real struggle at first. I still don't have the best abilities with Boolean Algebra..... but I'm down to my CPU and Decoder in MHRD now. (as well, I'm sure I can improve many of my chips).

If you feel you are getting close to your breaking-point, please don't give up. Make sure you have a Java Runtime Environment installed and check out LogiSim. Since it's written in Java you can run it anywhere (MAC, PC, Linux, etc...). It's a tool for building and simulating logic circuits.... I found it easy to pick-up and it's helped me a ton with visualizing my designs (and thanks to the simulator I can even do some sanity checking with it).

I'm sure if you stick with it you can get it.

For OR, I also encourage drawing it out on paper. And don't forget about the circuits you made prior to OR... often they're not the most efficient way to make a circuit, but they can be very handy to help reduce some clutter in diagrams that try to show every NAND... Then, once you have a circuit you understand that's drawn from things that include perhaps NOT, or AND (for example) you can re-drawn it as NAND gates if you want to look for any way to further optimize your NAND count.

Good luck!

[John]

Thanks for the advice man!

[Roxor128]

Here's my little hint: Remember how you made an AND gate earlier? What happens if you use the same techniques in different locations?