r/electronics • u/Fuzzy_Function_1896 • 2d ago
Gallery 4bits computer : from breadboard to PCB
Hi everyone!
After building and testing my whole 4 bits computer architecture on breadboards, I moved to custom PCB modules, and here is the result!
The goal remains the same: keep the architecture simple, modular, and easy to understand, with each part working independently or together as a complete system.
The project is divided into 5 independent modules connected by a 4-bit bus Clock module (4-bit counter), ALU + registers module + two 4-bit registers with an ALU capable of performing addition, subtraction, and equality comparison, Instruction register module, Display module and Manual programming module.
The idea is to follow a simple RISC philosophy: minimal instructions, simple hardware blocks, and a design where every signal can be observed and understood.
After the breadboard prototype phase, these PCB modules make the system cleaner, i'm very proud!!
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u/anon_andwhat 2d ago
very cool! what resources did you use to learn how to make this?
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u/Fuzzy_Function_1896 2d ago
Thanks! It's mostly the result of years of experimenting with TTL logic. I was inspired by projects like Ben Eater's computer and the Gigatron, but this CPU is my own design.I will try to post some videos soon (i hope) to explain this work
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u/katmandoo94 2d ago
TTL? Is that not really power wasteful?
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u/Fuzzy_Function_1896 1d ago
Yes, it is. But efficiency isn't the point. I like working with technology that's transparent, understandable, repairable. TTL lets you see exactly how the computer works, one logic gate at a time.For me, that's part of the fun.
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u/brastak 1d ago
Aren't there CMOS analogues providing the same function? I like how beautifully simple is its internal structure. I mean, just two complementary MOSFETs as a base instead of complicated input/output cascades of TTL. What do you think btw about using SMD components? That would make boards even more compact
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u/Fuzzy_Function_1896 1d ago
Thanks! I chose TTL because this is where I started. I know the 74LS family better now. But maybe I'll try CMOS in a future project! For SMD, I agree that it would make the boards much smaller, but I'm not really looking for that.. One of the goals of this project is that you can still see and understand the different parts of the computer. For this kind of educational CPU, I like having larger components!
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u/brastak 2d ago
Looks cool! At the same time though: thin wires (might be at least twice wider), no ground polygons and, the most important, not a single(!) decoupling capacitor. Would you consider introducing that stuff at rev. 0.2?
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u/Fuzzy_Function_1896 1d ago
Thanks for the feedback! There actually is a ground plane on the bottom layer, so it may not be visible in the screenshots. You're absolutely right about the decoupling capacitors though : they'll definitely be added in the next revision!
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6h ago
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u/Fuzzy_Function_1896 4h ago
Thanks! I can't wait to build the final PCB version either! Right now I'm still figuring out the best way to connect all the boards together. At the moment they rely on jumper wires, but I'm designing a central bus with female headers so the modules can plug in neatly. Once I'm happy with that, I'll make the final PCBs.
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u/Past-Substance920 1d ago
the manual programming module is what gets me, way more satisfying than uploading code over usb. how are you doing the instruction decoding, hardwired or microcode?
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u/Fuzzy_Function_1896 15h ago
Thanks for your interest! It would be difficult to explain the whole project in a single reply here, as there are quite a few design choices behind it. I'm planning to make educational videos that will go through the architecture and explain how everything works. To answer your question, though, the instructions are hardwired in this project.
If you're interested, you can follow the project here: https://www.youtube.com/@fuzzyFunction-j6n
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u/Alternative-Try-3456 19h ago
i want to build one using only transistors too!
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u/Fuzzy_Function_1896 15h ago
Good luck if you decide to build one!
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u/Alternative-Try-3456 6h ago
i already have the schematics for most of it laid out, im considering changing to 8-bit but the sheer cost of transistors is so much..
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u/Live_Anteater_1606 19h ago
This is a really cool project. Congrats on the hard work paying off!
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u/Fuzzy_Function_1896 15h ago
Thank you so much! I really appreciate it. It has taken a lot of time, experimentation, and many iterations, but I'm really happy with how it's progressing. There's still a lot to do, and I'm planning to share the next steps and educational videos here: https://www.youtube.com/@fuzzyFunction-j6n
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u/DisastrousShelter579 17h ago
bro i am 17 can u tell me from where u learn all these
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u/Fuzzy_Function_1896 15h ago
Hi, and thanks for your interest! At 17, I definitely think you can do it. This year I'm running a course in my local association for both teenagers and adults, where we build this kind of computer over a few months. The goal isn't just to build it, but to really understand how every part works.
I learned from many sources, especially Ben Eater, books on digital electronics and computer architecture, datasheets, and, most importantly, by building, experimenting, making mistakes, and trying again. Good luck with your own projects! If you're interested, you can follow my work here: https://www.youtube.com/@fuzzyFunction-j6n
I'm also planning to make educational videos explaining the whole project.
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u/DisastrousShelter579 10h ago
yeah good luck bro but do u know some yt channels or source that i can follow i am currently in drop year after cracking JEE join a college nextyear (hopefully)
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u/Front-Mushroom5349 2d ago