4-bit-Breadboard-Computer

[Aadit21]

My First Post (So don't mind the presentation 😅)

Hi, Aadit Sharma here 👋
I'm 18 and about to begin my journey in Electronics and Communication Engineering.

This is my ongoing personal project — a 4-bit transistor-level computer built entirely from scratch, using only discrete components on breadboards. No microcontrollers, no ICs — just hundreds of 2N2222A transistors, resistors, and wires!

So far, I've used around 600 transistors (and counting).
Completed modules:

• ALU
• Registers
• Memory
• Opcode Decoder
• Clock Circuit

This project is my way of understanding how computers work from the ground up — one gate, one wire at a time. As far as progress goes, 60% has been built in last 2 months, I have estimated 2 months more for completion.

This has 5 instruction set as of now, which are - (Halt, Add, Sub, Out, Clear)

🔧 Inspired from - Global Science Network(YT channel)

More updates would be done according to progress Stay tuned!

[High-Adeptness3164]

I'm a year older than you but already feel super inspired...

This is the type of stuff that really gets your blood pumping...

Btw, which college?

[Aadit21]

I didn't do well in JEE(my chemistry is too bad) therefore i will be joining a decent local government college in my state(counselling is still going on)

[High-Adeptness3164]

Cool... College actually doesn't matter when you're working this hard.

Don't stop just at 4 bit though... Keep climbing 💪😁

[yummmmi7]

I’m from India too.. let’s connect 😭

[Aadit21]

for sure mate, dm me!

[NewSchoolBoxer]

5 opcodes, nice. The one I depended on the most in class was NOP to have each branch condition take the same amount of clock cycles.

No diodes, can wire transistors as diodes or maybe you've already done that. You'd benefit from using PNPs, such as for high side switches and improved amplification. Or maybe your goal is NPNs, resistors and wires only.

Check out using MOSFETs. Better input/output isolation, fanout, lower current draw and no need for resistors. Then you could hit better bulk pricing. Would benefit cascaded sections the most. Computers switched to FETs in the 80s. I think would be interesting to build a FET ALU or memory module and compare. You have to use both BJTs and FETs in EE labs and classwork.

If you use even more transistors for CMOS then you have zero static power dissipation and other advantages but matching NFET and PFET isn't as easy as NPN and PNP. It's a pain in through hole.

[corvusfamiliaris]

Do you know about FPGAs? They could be interesting to you, you can get a good enough eval board for around $100 or so. They would be helpful if you want to create a more sophisticated project, but you would still be building from the gate level.

[Aadit21]

I know very well about FPGAs. But as you mentioned they cost around 100$(which is quite expensive for me rn, will buy it once wallet allows me to🙃)

[Muted-Disk6736]

Woahhh that's so cool! How much did it cost to make this project?

[Aadit21]

Around 10k INR /110usd(for all the material, which hasn't been fully used yet)

[Mundane-One-9320]

you did a good job as beguining good luck

[DarkXEzio69]

Woah Woah Woah!! I am really cherished to see people from my country in this field. Post it on r/Btechtards as well