Developer launches SIMH emulator to preserve French Mitra-15 minicomputer

Developer JPLeRouzic has released a preliminary simulator for the Mitra-15, a vintage French 16-bit minicomputer, as a branch for the SIMH emulator. The project seeks to preserve the computing history of the Compagnie Internationale pour l'Informatique (CII) system, an architecture for which very little documentation and software have survived.

The current implementation is based on a modified SDS 940 simulator for SIMH. According to the project's documentation, the simulator already includes a complete instruction decoder for every instruction and addressing mode, alongside a rudimentary, though currently untested, assembler. To refine the simulation, the developer is actively seeking additional documentation and memories from former users of the system.

A Pillar of French Computing

Developed by CII in the early 1970s, the Mitra-15 was a versatile 16-bit minicomputer deployed across several critical sectors. It saw widespread use in industrial automation, scientific computing, education, and military applications. Technically, the Mitra-15 was distinguished by its ability to program I/O peripherals using microcode, bypassing the need for external mechanisms such as Direct Memory Access (DMA).

This hardware was part of a broader strategic effort by the French government and CII to establish a domestic computing industry. While the Mitra-15 was once a common sight in French technical installations, the hardware eventually became obsolete. Over time, the associated software ecosystem largely vanished, leaving a void in the historical record of European computing.

The Stakes of Digital Archaeology

This project represents a significant effort in digital preservation. By recreating the Mitra-15 within the SIMH framework, the developer is building a platform where the few remaining fragments of original CII code can be executed and studied. Without such emulation, the specific architectural nuances of this era of European computing face total loss.

"Although it was once widespread in France, very little software and documentation has survived," JPLeRouzic stated. "This project contributes to the preservation of this important part of computing history."

Future Development

Beyond the core simulation, the developer is attempting to reconstruct CII's MTR (Real-Time Monitor) using a hexadecimal dump sourced from a PDF with poor OCR quality. There are also long-term ambitions to port RSX280, an RSX-11 clone, to the Mitra architecture. For now, the project remains a work in progress, relying on the discovery of lost manuals and the recollections of the original user base to achieve full accuracy.