How One Maker Hand‑Welded a Fully Functional CPU from Scratch

A recent B‑site video showcases a creator who spent half a year hand‑soldering a complete CPU from discrete components.

Pure! Hand! Made! Custom CPU

The creator, nicknamed “Milk‑flavored”, used only diodes, transistors, and resistors to build the processor.

He first tackled the register section, designing a 6‑bit shift register that can store data and shift it left or right under clock control.

The shift register acts like a traffic cop, directing data flow based on clock signals.

Next, he implemented the program counter (PC) , which records the current execution address. This module took about three months to complete.

For memory, he used the HM628512 chip to provide both ROM and RAM functions.

He then added an instruction decoder to translate incoming CPU instructions into control signals.

The arithmetic‑logic unit ( ALU ) was integrated next to perform basic arithmetic operations.

A small cache was also soldered onto the board.

Beyond hardware, the creator wrote the CPU’s instruction set directly in binary, a process he called “ancient programming”.

Pure hand‑written binary programming!

Initial runs were unstable; a broken connection caused the LED‑based test pattern to fail. After fixing the wiring and adjusting jump instructions, the CPU finally displayed a steady running light sequence.

The project consumed over 1,000 transistors, 2,000 diodes, and roughly 2,000 resistors, with nearly ten thousand solder joints and a cost of about 1,000 CNY. The creator likens the process technology to a 2.54 mm “process node”, humorously comparing it to modern 3 nm chips.

He plans to continue expanding the CPU’s capabilities to run more complex programs.

Creator Background

The maker, named Lin Nai‑wei from Beihai, Guangxi, was inspired while analyzing binary executables. He started from basic analog circuits, gradually designing gate‑level modules without any professional equipment, using only LEDs and buzzers for testing.

His ultimate goal is to understand CPU operation from the ground up, tackling challenges such as inter‑module connections and clock speed (approximately 100 kHz).