A virtual DOS machine that runs legacy 16-bit DOS applications on various platforms
Author: Xu Ha ([email protected])

As far as we know, Microsoft Windows no longer supports 16-bit MS-DOS application and they removed NTVDM, since virtual 8086 mode is not available under amd64 extended mode. This project aimed at building a virtual dos machine for 64-bit Operating Systems.

The idea of this project is to emulate a 16-bit CPU and provide BIOS/DOS interrupt services to MS-DOS applications. In NKVDM, 16-bit applications runs as before in 32-bit Windows. We want to create a compatible environment for 16-bit applications, for example, applications can access disk files on host machine using legacy DOS interrupts instead of using network sharing.

Now we already have a PC emulator which could run in Win32 console and it supports all 8086 instructions - MS-DOS 6.22 runs well inside this PC emulator. The only work left for this project is to construct the built-in dos kernel for the emulator, so that it can load dos executables and execute them under any available platforms. Please visit the homepage of NXVM project at https://github.com/cshaxu/nxvm.

Currently I am learning the MS-DOS internals and here's the roadmap.

Collect all INT services dealing with Disk
MS-DOS Read/Write To Host Machine Disk/Files
Keep io.sys, msdos.sys and command.com in disk image

Collect all Exec related interrupt services
Learn about DOS Kernel
Load and execute command.com from host machine
Keep io.sys and msdos.sys in disk image

Implement Dos Kernel in C and load it into NKVDM
Keep io.sys in disk image

Move io.sys out of disk image
Implement Dos IO in C for NKVDM
Remove disk image and NKVDM runs without MS-DOS support

Copy source files from NXVM project (version 0.4.015d or higher) to NKVDM source folder:
nxvm/src/ -> nkvdm/src/nxvmsrc/

For Windows,
Add the files to the NKVDM project settings and compile.

For Linux/UNIX,
Simply use automake scripts:
./configure
make