How a DIY Enthusiast Built a Fully Functional CPU from Old Memory Chips

Majsterkowanie i nie tylko (MINT) showcased EPROMINT, a hand‑crafted 8‑bit processor assembled using a soldering iron, vintage memory chips, and classic 8‑bit logic devices, achieving full instruction execution and memory addressing without any modern ICs.

The CPU was connected to a VFD display and ran custom‑written assembly code, even playing a low‑resolution clip of "The Matrix".

MINT open‑sourced the entire project on GitHub, providing schematics, firmware, design documents, and an instruction‑set specification.

Development began with a simple ALU supporting addition, which was iteratively redesigned into a more powerful, slot‑based ALU. Subsequent modules added included a memory‑control unit, an I/O and program‑storage module, and a control unit for instruction scheduling.

Interrupt handling was implemented: on an external event the processor pushes the program counter onto a stack, jumps to an interrupt service routine, and restores the PC after execution, enabling responsive button inputs.

Beyond basic operations, the CPU performed complex tasks such as PWM motor control, LCD text display, ASCII conversion, and even 24 fps video output via precise division loops.

Future plans involve writing a C compiler for EPROMINT to allow higher‑level programming.

The project sparked community excitement, with many praising its pure DIY spirit and the demonstration of computing fundamentals using only legacy components.