Ryo Mukai's 4004 Single-Board Computer Is a Love Letter to Intel's Historic First Microprocessor

Vintage computing enthusiast Ryo Mukai has reached back to the very early days of microprocessors for a single-board computer design based on Intel's iconic 4004 — and offering 8080 emulation and a Very Tiny Language (VTL) for on-device programming.

"This is a home-brew [Intel] 4004 experimental board, and an 8080 emulator running on the board," Mukai explains of his creation. "Palo Alto Tiny BASIC worked with minor modifications. I have made [a] PCB with 64kB of memory and have done initial operation checks."

The heart of Mukai's design is the Intel 4004, a real piece of history. Released in 1971 and not discontinued until a decade later, the 4004 was the world's first commercially-produced microprocessor — and kick-started Intel's processor business. Based on a four-bit binary-coded decimal instruction set, the DIP-packaged part has a mere 2,300 transistors and runs at a somewhat sluggish 740kHz at launch — but its place in the annals of computing is most definitely assured.

Although originally designed for use in a calculator, the Intel 4004 was a true general-purpose processor — and, as if to prove that point once again, Mukai's creation is a fully-functional single-board computer built around it. As well as the 740kHz four-bit Intel 4004, the board includes an 8kB ROM with 3.75kB available to the user, 4kB of RAM on the breadboard version expanded to 64kB on the PCB variant, and a 9,600 baud serial port.

The board's capabilities also include a monitor, support for a Very Tiny Language (VTL) interpreter, and the ability to run Palo Alto Tiny BASIC — all of which allows for on-device programming. There's even support for emulation of the Intel 8080, Intel's second-generation eight-bit processor and successor to the 8008 — itself the successor to the 4004 — though Mukai admits the emulation "is very slow" and could benefit from tuning.

Hardware design files and source code are available on the project's GitHub repository under the permissive MIT license, with more information to be found on Mukai's blog.