Linux boots in 4.76 days on the Intel 4004
The long, slow boot
To make Linux on the 4004 work, Grinberg had to overcome numerous challenges. The 4004 has extremely limited ROM and RAM, no interrupts, and lacks even basic logical operations like AND and OR. Grinberg’s emulator makes clever use of lookup tables and other tricks to squeeze maximum performance out of the primitive CPU.
The final hardware uses the 4004 (overclocked to 790 kHz) along with several other period-correct support chips from Intel’s MCS-4 chipset. It includes a VFD display to show Linux output and can accept input over a serial connection. The whole setup draws about 6 W of power.
To pull it all together, Grinberg designed a custom circuit board with no vias (paths from one side of the circuit board to the other) and only right-angle traces for a retro aesthetic. It’s meant to be wall-mountable as an art piece, slowly executing Linux commands over the course of days or weeks.
While it has no practical purpose, the Linux/4004 project demonstrates the flexibility of Linux and pushes emulation to its limits. Grinberg is considering the possibility of offering kits or fully assembled boards for others who want to experience Linux at its slowest, though this is not yet definite.
The full details of the project, including schematics and source code, are available on Grinberg’s website. For those interested in vintage computing or extreme Linux implementations, it’s a fascinating look at what’s possible with 1970s technology and a lot of clever engineering.
