Dubna BESM-6 Emulator

Run programs from a 1970s Soviet supercomputer on your laptop — complete with the original Russian-language output.

The BESM-6 was the flagship Soviet computer of the 1960s–70s, widely used at research institutes across the USSR. At the Joint Institute for Nuclear Research in the city of Dubna, scientists ran their calculations under the Dubna monitor system — a home-grown operating system described in the book Программирование на БЭСМ-6 в системе "Дубна" by Gennady Maznyi.

This emulator recreates that system faithfully: you feed it original job files and get the original output — Cyrillic banners, Fortran listings, plotter graphics, and all.

make
make install
dubna examples/name.dub

Read job 'name.dub'
Mount image '/Users/vak/.besm6/9' as disk 30
Redirect drum 21 to disk 30
------------------------------------------------------------


                                         3  000    00.00
 ЙОКСЕЛ      БЭСМ-6/5     ШИФР-12
 МОНИТОРНАЯ СИСТЕМА  ′Д У Б Н А′  -  20/10/88




         ЖЖЖЖЖ ЖЖЖЖ  Ж   Ж Ж   Ж ЖЖЖЖ  ЖЖЖЖ
         Ж   Ж Ж   Ж Ж   Ж ЖЖ ЖЖ Ж     Ж   Ж
         Ж   Ж Ж   Ж Ж   Ж Ж Ж Ж ЖЖЖ   Ж   Ж
         Ж   Ж Ж   Ж Ж  ЖЖ Ж Ж Ж Ж     Ж   Ж
         Ж   Ж ЖЖЖЖ  Ж Ж Ж Ж   Ж Ж     ЖЖЖЖ
         Ж   Ж Ж     ЖЖ  Ж Ж   Ж Ж     Ж
         Ж   Ж Ж     Ж   Ж Ж   Ж ЖЖЖЖЖ Ж


*NАМЕ ПРИМЕР
*ЕND FILЕ
------------------------------------------------------------
   Elapsed time: 0.007 seconds
      Simulated: 209161 instructions
Simulation rate: 30269320 instructions/sec

The examples/ directory contains over 100 ready-to-run programs:

• Languages: Fortran, Algol, Pascal, BESM-6 assembly, the B language
• Games: Adventure, Wumpus, Oregon Trail, Hamurabi, and more
• Graphics: Mandelbrot set, 3-D surfaces, parametric curves — rendered as SVG via simulated Calcomp, Tektronix, and Watanabe plotters
• Curiosities: Quine programs (self-reproducing code in multiple languages), π calculation, character encoding demos

See examples/README.md for the full catalog with descriptions.

• C++17 compiler (GCC 7+, Clang 5+)
• CMake 3.12+
• Git (used to fetch the test framework at build time)

# Standard build
make
make install

# Debug build
make clean
make debug
make

The system tapes (Dubna monitor, standard libraries, assembler) are embedded in the binary — no separate download is needed to run examples.

dubna [options] filename.dub

A .dub file is a job script for the Dubna monitor system — think of it as a shell script that sets up libraries, specifies the programming language, and provides the source code or data for one run.

Pass one or more letters to -d:

Examples:

# Run with verbose output
dubna -v examples/fortran.dub

# Trace instructions and registers to a file
dubna -d ir --trace=debug.log examples/name.dub

# Stop after one million instructions (useful for debugging loops)
dubna -l 1000000 examples/name.dub

The emulator looks for disk images in this order:

1. Current directory
2. ~/.besm6/
3. /usr/local/share/besm6/
4. Directories listed in the BESM6_PATH environment variable

Disk images use the SIMH format (the same format used by other vintage computer emulators). The core system tapes — Dubna monitor, Fortran/Algol/Pascal compilers, the BEMSH assembler — are built into the binary and mount automatically.

make test          # 127 tests, ~0.6 seconds
make test-all      # includes optional CERN library tests

See tests/README.md for details on test categories and how to run individual tests.

The BESM-6 used a 48-bit word, with 32 768 words of memory organized in 1 024-word pages. The CPU had a 15-bit program counter, a 48-bit accumulator, an auxiliary 48-bit register (RMR), and 15 modifier registers used for address arithmetic. System services — file I/O, math functions, job control — were invoked through a special instruction class called extracodes (think system calls). I/O devices included magnetic drums and disks, a punch-card reader/puncher, and pen plotters.

The emulator is written in C++17 and structured as: Session (public API) → Machine (orchestrator) → Processor + Memory + I/O devices + extracode handlers.

For a full description of every CPU instruction, see doc/Besm6_Instruction_Set.md.

See TODO.md for a list of known issues and planned improvements.

MIT — see LICENSE.

• Gennady Maznyi — author of the original Dubna programming book
• Mikhail Popov — keeper of invaluable knowledge about the Dubna operating system
• Leonid Broukhis — original emulator development
• Serge Vakulenko — current maintainer
• BESM-6 Community — historical documentation and software preservation