nd100x

ND-100/CX Emulator written in C

For more information about the ND-100 series of minicomputers: https://www.ndwiki.org/wiki/ND-100

Origins

This project (nd100x) is a fork of nd100em, started in 2025 by Ronny Hansen. It remains under the GNU General Public License (GPL v2 or later).

This project is based upon the source code from the nd100em project. Their latest version was version 0.2.4, which can be found here https://github.com/tingox/nd100em Read more about the nd100em project here https://www.ndwiki.org/wiki/ND100_emulator_project

The original authors of the nd100em are:

• Per-Olof Åström
• Roger Abrahamsson
• Zdravko Dimitrov
• Göran Axelsson

Status

The emulator is under active development. Current work in progress includes:

• All test programs validate the CPU, Memory Management and Devices.
• Missing some opcodes around BCD
• Boots SINTRAN L from SMD in 6-7 seconds on my machine.

Improvements

This project continues from nd100em version 0.2.4 and includes significant enhancements:

• Opcode Improvements
  • Added support for missing opcodes
  • Fixed bugs in several instructions
• Memory Management
  • Fully re-implemented with support for MMS1 and MMS2
  • Proper TRAP generation for Page Faults and Access Violations
• IO Subsystem
  • Complete rewrite: now single-threaded and simplified
  • Old IO code has been removed
• Supported IO Devices
  • Real-Time Clock (20ms tick emulation pending for full SINTRAN compatibility)
  • Console
  • Floppy (PIO and DMA) for 8" and 5.25" formats
  • SMD Hard Disk (75MB; multi-drive support in progress)
• Codebase Modernization
  • Removed requirement for libconfig and the supporting .conf file. All options are now given on the command line.
  • Refactored folder structure
  • Automatic function header generation via mkptypes (by Eric R. Smith)

Project Goals

• Focus on ND-100 CPU and controllers.
  • The newer CPU's (ND-110 and ND-120) is mostly hardware/performance improvements, with some new opcodes to support SINTRAN and COBOL running with better performance.
  • Focus on getting these opcodes into this emulator has very low priority, as SINTRAN doesnt require an ND-110 or ND-120 CPU.
• Refactorand, re-structure and modernize code so its easier to extend
• Adding support for building different frontends
  • The only frontend currently is the nd100x emulator
  • Other frond ends planned
    • Web Assembly version (WASM) for running emulator in browser and in Visual Studio Code as plugin
    • Arduino, ESP and RISC-V device support.
    • Emulator with debug interface
    • Windows version
• Adding even more devices (like HDLC, Ethernet, SCSI)

Project Structure

The project is organized into several key components:

• src/cpu/ - CPU emulation implementation
• src/devices/ - Device emulation (I/O, peripherals)
• src/machine/ - Machine state and main emulation loop
• src/ndlib/ - Supporting library functions (loading BPUN and a.out formats++)
• src/debugger/ - DAP Debugger supporting functionality
• src/frontend/ - User interface and emulator frontend(s)
• tools/ - Development and build tools
• images/ - Norsk-Data SMD disk, floppy and BPUN files.
• build/ - Build output directory

Build Requirements

• Linux (I am using Ubuntu 22.04) under WSL
• GCC compiler (I am using GCC 11.4.0)
• Make build system
• mkptypes tool (automatically built during compilation)

Additional Dependencies for Floppy Menu

The floppy menu functionality requires additional libraries:

• libcurl4-openssl-dev: For downloading floppy database from the internet
• libncurses5-dev: For the terminal-based user interface

Install these dependencies on Ubuntu/Debian:

sudo apt update
sudo apt install libcurl4-openssl-dev libncurses5-dev

On FreeBSD

pkg install curl ncurses

Note: The floppy menu requires an internet connection to function properly.

Note 2: The floppy menu is disabled on RISC-V and WASM builds.

Building the Project

1. Clone the repository:

git clone https://github.com/HackerCorpLabs/nd100x.git
cd nd100x

git submodule update --init --recursive

2. Build the project:

• For debug build (default):

make debug

• For release build:

make release

• For build with sanitizers:

make sanitize

• For more information on the build system, see the How to build document.
• Support for WebAssembly builds has been added, for more information see the How to build WASM document
• Support for Risc-V builds has been added, for more information see the How to build RISC-V document

Updating Git submodules

Sometimes the submodules are updated and you need to manually refresh them

• git submodule update --init --recursive

Command Line Options for nd100x

The emulator supports the following command line options:

Usage: nd100x [options]

Options:
  -b, --boot=TYPE    Boot type (bp, bpun, aout, floppy, smd)
  -i, --image=FILE   Image file to load
  -s, --start=ADDR   Start address (default: 0)
  -a, --disasm       Enable disassembly output (dump after emulator stops)
  -d, --debugger     Enable Enable DAP debugger
  -v, --verbose      Enable verbose output
  -h, --help         Show this help message

Examples:

  build/bin/nd100x -b aout -i a.out -v -d    # Loads an a.out file from the current directory in verbose mode and enables disassembly

  build/bin/nd100x -b bpun -i images/FILSYS-INV-Q04.BPUN      # Loads the latest version of FILSYSTEM INVESTIGATOR (Version: Q04 - 1987-10-10)
  build/bin/nd100x -b bpun -i images/CONFIGURATIO-C08.BPUN    # Loads an old version of CONFIGURATION-C08
  build/bin/nd100x -b bpun -i images/INSTRUCTION-B.BPUN       # Loads an old version of INSTRUCTION VERIFIER

  build/bin/nd100x -b floppy                                  # Boots from a floppy file named FLOPPY.IMG
  
  

Boot Types:

• smd: SMD disk boot (default)
• bp: Boot program
• bpun: Boot program unprotected
• aout: BSD 2.11 a.out format
• floppy: Floppy disk boot

Block devices (Floppy and SMD)

Currently the file names used for floppy and SMD are hard coded. And the files are expected to be in the current folder.

• Floppy drives uses FLOPPY.IMG
• SMD drives uses SMD0.IMG, SMD1.IMG, SMD2.IMG and SMD3.IMG.

Other floppy images can be mounted via the Floppy Menu

Running SINTRAN in the Emulator

The emulator requires a system image file (SMD0.IMG) to run. Place the image file in the project root directory.

To boot a SINTRAN image from an SMD disk

build/bin/nd100x --boot=smd 

Read more about how to boot sintran

Booting TPE-MON from floppy and running test programs

The emulator requires a floppy image to boot from. Place the image file in the current directory.

cp images/Nd-210523I01-XX-01D.img FLOPPY.IMG
build/bin/nd100x --boot=floppy

Now you have access to test programs like CONFIG, PAGING, INSTRUCTION and more.

Floppy Menu

The emulator includes a built-in floppy disk browser that allows you to browse and mount floppy disk images from the ND100 floppy database.

Accessing the Menu

While the emulator is running, press F12 to open the floppy menu.

Menu Features

• Browse Database: View all available floppy disk images from the online database
• Search Functionality: Search for floppies by name, reference, or directory content
• Detailed Information: View detailed information about each floppy including description, reference and directory content
• Mount Capability: Mount selected floppy disks to floppy drive units 0, 1 or 2

Requirements

• Internet connection (required to download floppy database).
• Terminal that supports F12 key

Floppy database is available directly at https://ndlib.hackercorp.no/

Assembling your own programs

Using the assembly tool from Ragge nd100-as you can compile ND assembly to a.out format and load into the emulator.

This assembler is following the AT&T syntax so it differs a bit from the ND-100 MAC assembler.

lda foo
sta bar
opcom


bar: .word 11
foo: .word 22

Remember to end your code with 'opcom' to make the emulator stop executing your code.

Overview of all assembly instructions

Multiple systems

The nd100x emulator has been compuiled and tested on multiple different systems. For more information, read the Tested systems document

License

See the LICENSE file for detailed licensing information.

Contributing

See the CONTRIBUTING.md file for more information

TODO

• Refactor IO access to request BLOCKs from Machine instead of direct file access
  • Opens up for running WASM in the browser
• OPCOM implementation
  • Emulation of OPCOM for memory inspection when CPU is in STOP mode.
  • Currently STOP mode exits the emulator
• Clean up code and standardise on 8,16,32 and 64 bit signed and unsigned names for types