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Digital Logic Sim

​A minimalistic digital logic simulator · By Sebastian Lague

YT playlist for community creations Sticky

A topic by Sebastian Lague created Apr 17, 2025 Views: 7,313 Replies: 94
Viewing posts 1 to 44
Developer (2 edits) (+7)

Hi everyone, I was thinking it might be fun to have a playlist on youtube to showcase different things that people have built  in the simulation. So if you have something you want to share, just upload a video to yt and drop the link here. Don’t worry about it having to be super elaborate or anything, I think it’s cool to see a variety of projects, both small and large. There’s also no time limit to this — I’ll check back every so often and add any new entries to the list :)

If you want to check it out, you can find the playlist over here.

(By the way, I’m also planning to show some of these  in a video — most probably at the end of my digital logic series. That’s still quite a while away, but I’ll link that here as well once it’s eventually out).

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I implemented an 8-bit CPU similar to Ben Eater's! So far it's only programmed to count down by tens and then stop on overflow, but it's a start!

Developer

Very nice, thanks for sharing! I've made a playlist now over here. Will share it more widely once there's some more stuff in there :)

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I've been using ver.1 since it came out. I need an android version if this. Please, please, and thank you.

theres now an android version. :D

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I made a pseudo random number generator

Developer

Cool! Would be fun to see with the rgb display as well

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Good idea!

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me too

Hey, Can you add OpenGL support?. My computer cant run V2 because your using D3D12, ,My computer supports up to D3D10

Maybe try updating your graphics drivers?

maybe he has an old (like really old) gpu for some reason?

Hey, i am working on a completely custom cpu in the Simulator, can anyone give me ideas and maybe tips and stuff i need for it? I know, probably not the right place to ask haha

I don't know what could I make since I have no idea how to make something here, but it would be great to see someone making a 1080p display lol

oh cool great idea, i cant do it sadly because idk how to use rgb display

me too lol

its like ram. the 8-bit input is the address/location and the 3 4-bit inputs are data/color for the pixel/ mem address. reset clears it all, write is store, refresh is to show what you wrote and clock is, well just a clock input like in the vids

(1 edit) (+1)

ok, so, i also made a CPU with my own architecture. If anyone cares i'll upload the project and instructions

Developer(+1)

Very nice!

You're so cool

good, make a gameboy maybe??

this is my first time using the rom thingy

fyi i use canva

I kept it simple, I made a bouncing ball : 

Choose your next challenge:

  • Give it gravity
  • Use RGB Display to:
    • Make it change color every time it bounces
    • Allow the user to change it's color
  • Make it bigger, or:
    • Make a customizable size
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Then let's try gravity..

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I made a simple CPU 

Developer

Awesome work :)

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I made a 8kB memory with RGB display and printed out color gradients with those.

Great Job, but would it really have been that hard to make some neater wires?

Well, I quickly wired the outside part of the memory since it was just for demo purposes. But I can hardly do any better with the inside.

Its still fine

I, myself, like making my wires all neat. In fact, I enable snap to grid while grid is shown so I don't have to hold down control. Yes, it does take much longer than just going straight from the output of one chip to the input of another chip, but the benefit is that it's clean and readable (and much easier to debug if something were to go wrong).

Developer(+1)

Nice!

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Hello SebastianI have an entire playlist dedicated to your simulation. I'm a computer engineering student in Brazil and I run an educational channel where I talk about science and technology. I built a complete PC using a variation of the SAP (Simple-As-Possible) architecture, which I plan to post on YouTube soon. Here's the playlist if you'd like to take a look:

https://www.youtube.com/playlist?list=PLWESPp1qoWOUfivqt1nj0kn5Kni6txcyh

Great work, by the way! I used the simulator to teach my entire class about the subject, as well as some subsequent classes.

Developer(+2)

Hey, that's very cool -- thanks for sharing!

Hello you can use my Digital Clock from V1 here 

If someone's out of ideas, here's one: a calculator. 2 8-bit inputs to input 2 numbers and 2 1-bit inputs to choose an operation (e.g. 01 - addition, 01 - subtraction, 11 - division and 0 - multiplication) and one 1bit input to perform the calculation.

yeah i am working on that.... ;) but more complex one with functions like sin cos tan sqrt ... but it will take some time... 

You can store the sin cos, and sqrt with the ROM I believe

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Hey, I made a 8 Bit CPU, desinged a custom Instruction Set, created my own Compiler and then coded Snake to run on it.
Here's my showcase: I built a Computer and ran Snake on it*

Developer

Very nice! Thanks for sharing

Nice, I just finished a similar thing

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I made a Computer and Compiler a link to its post is Here.
Developer

Nice work!

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Here's my basic 8-bit computer where I'm trying to keep elements as exposed as possible while also still keeping it tidy. More info in this thread.

Developer(+1)

Very cool!

using Buzzers i created the super mario theme song.

Very cool. All you need now is the delay for each note.

I made Conway's Game of Life in the Digital Logic Simulation. It works by cycling over each cell in the grid and checking if it it on with 2 or 3 cells around it on or off with 3 cells on around it, if either of these conditions are met it writes that cell on otherwise, off. After every cell has been set it refreshes and loops. I used 8 hidden dot displays so that it can check all of the neighbours at once. Right now it is only a 16x16 screen, I am considering upscaling but it takes 6 ticks per cell, so increasing size increases time. If you have suggestions on how to make it better, let me know.
Project Files

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I am trying to create as many 74 logic chips as i can from my TTL cookbook. can i share the library once i have finished so other people designing a 74 logic based cpu can use my chips?

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What do you mean? This is the post to share videos, not asking questions.

(1 edit) (+2)

Inspired by the guy two posts above me, I decided to also build my own version of Conway's Game of Life:

Developer

Awesome!

HEREs MY VID MY VIDEO

Its the same one thats added to the playlist right?

yes

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HERES another vid 

if anyone needs this: for a very very fast clock you can take 2 not gates: the first out feeds to the second out, and first and second out go to the output to create a flickering stage.

Or a xor gate, the output goes into it self while the other input is fed by a not or a input

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heres a 3rd vid. This time in v0
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another one

I have made a 7-segment-display tutorial

(1 edit) (+1)

I've been working on this one for a while now. PONG!

I have more details in this thread: https://itch.io/t/4920753/pong-8-bit-computer

Seb, if you want to use any part of this for your program or videos, go ahead.

Developer(+1)

Extremely cool, thanks for sharing!

how can you make output wires diffrently from normal

If you mean the color, just right-click on the output.

Thanks!

Right+Click on an I/O pin to change the name or the color of the wire that connects to it. The same can be done for the output pin of a chip, but only the wire color.

Thanks!

NEW VIDEO WITH SCROLLING HERE IT IS youtube.com/watch?v=reX6NL3gVyU

(1 edit)

new vid 

also can you add my other vids

I made the BCD you made in your old video (visualizing data) and improved upon it (and also modernized it) (since V2 doesn't have an actual negative sign and instead turns the display blue which doesn't really show that the number is negative), I made my own negative sign using the G segment.

I have found one flaw in my design. I didn't actually account the fact that the number might not actually be negative while in two's compliment. I did address this. I'll share an updated video later.

After playing around with your Buzzer chip, I got a general idea of how it works now.

Lowest note (0): A0 (27.5 Hz), Highest note (255): A#7 (3729.310092 Hz), each value steps up by 1/3 of a semitone (meaning 3 = A#0, 6 = B0, 9 = C0, and so on). The buzzer sound seems to be a simple square wave too...

This gives me an idea, which may take me a while to make...

I made a piano, from c4 to c5

Cool. I have something bigger in mind. ;)

Not really a showcase of something I build in the Sim, but rather an Upgrade on the Sim itself, but I think it's still kinda neat:

My pull request is here.

I did some testing and found that I'm able to play multiple buzzer noises at once. I also took the liberty of converting all of the different note names to hexadecimal to make it easier for me to encode a short tune...

Unfortunately, I'm on a Mac, where I am unable to record my internal audio since QuickTime doesn't even support it. It can only record external audio. And I'm not the kind of person who would download alternate software just to be able to do it as they might not even be safe.

I got an idea that might just work... I'm gonna use my phone to record the audio, and the Mac to capture my screen. Then all I need to do is try and sync them up as best I can.

you could use obs

Is it free? I don't use paid programs to do simple tasks.

OBS - Open Broadcaster Service

It's obviously free, you could also check the website... Anyways, it does require a tiny amount of setup so youtube tutorials are probbaly good idea

(1 edit)

Just downloaded it. Was very easy to setup, no tutorials needed. I have it set to display capture instead of application capture, but I'll likely switch to that. If I somehow forget, I can always just crop to the application window in post editing.

I also found a bug with OBS. Apparently if you hide OBS from capture, the Stop Recording button will bug out and only capture 1 to 5 seconds of video, even though I was recording for like 40 seconds. unchecking "hide OBS from capture" fixed that issue.

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I had to do it. I created Bad Apple with your simulation. 

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Finally got the video with audio. Video also showcases my updated BCD circuit.

https://youtu.be/jbQVq1o8YEY?si=FiLdHfUe_L5MNpNl

i have a new video 

(2 edits)

I created a simple 4-bit random number generator. I use a 4-bit adder cycle through the numbers from 0-15 and use 4 Data Latches and 4 3-state buffers to output the adder when the enable signal is on. This is my first attempt. 


My own CPU named "N-16" executing Fibonacci sequence (23 Numbers and one overflowed number)

I made a 4-bit CPU for fun here, it just needs RAM but other than that it works pretty good.

( Sorry for the bad video quality, I saved it in 1080p but idk what happened here haha )

Your video quality is fine, it just takes a while for the higher quality part to finish processing.

For the XOR chip, you can actually make one using only 4 NAND chips: the first NAND is connected to both inputs, the second is connected to Input A and the output of the first NAND, the third is connected to Input B and the output of the first NAND, and the outputs of the second and third NAND chips go into the inputs of the final NAND, and the output of that is the final output.

Yes I actually know that, but that was only after I finished the CPU haha ! :D

I'm making Tic-Tac-Toe in DSL.

Yes, you read that right, I'm making a fully functional Tic-Tac-Toe game in Digital Logic Sim. I got the input part figured out. Here's a sample:

I am amazed yet scared of what people can do with a game that seems so simple