v86 emulates an x86-compatible CPU and hardware. Machine code is translated to WebAssembly modules at runtime in order to achieve decent performance. Here's a list of emulated hardware:

• An x86-compatible CPU. The instruction set is around Pentium III level, including full SSE2 support. Some features are missing, in particular:
  • Task gates, far calls in protected mode
  • Some 16 bit protected mode features
  • Single stepping (trap flag, debug registers)
  • Some exceptions, especially floating point and SSE
  • Multicore
  • 64-bit extensions
• A floating point unit (FPU). Calculations are done using the Berkeley SoftFloat library and therefore should be precise (but slow). Trigonometric and log functions are emulated using 64-bit floats and may be less precise. Not all FPU exceptions are supported.
• A floppy disk controller (8272A).
• An 8042 Keyboard Controller, PS2. With mouse support.
• An 8254 Programmable Interval Timer (PIT).
• An 8259 Programmable Interrupt Controller (PIC).
• Partial APIC support.
• A CMOS Real Time Clock (RTC).
• A generic VGA card with SVGA support and Bochs VBE Extensions.
• A PCI bus. This one is partly incomplete and not used by every device.
• An IDE disk controller.
• An NE2000 (8390) PCI network card.
• A virtio filesystem.
• A SoundBlaster 16 sound card.

Demos

Arch Linux — Damn Small Linux — Buildroot Linux — ReactOS — Windows 2000 — Windows 98 — Windows 95 — Windows 1.01 — MS-DOS — FreeDOS — FreeBSD — OpenBSD — 9front — Haiku — Oberon — KolibriOS — QNX

Compatibility

Here's an overview of the operating systems supported in v86:

• Linux works pretty well. 64-bit kernels are not supported.
  • Damn Small Linux (2.4 Kernel) works.
  • All tested versions of TinyCore work.
  • BuildRoot can be used to build a minimal image. humphd/browser-vm has some useful scripts for building one.
  • Archlinux works. See archlinux.md for building an image.
  • Debian works. An image can be built from a Dockerfile, see tools/docker/debian/.
  • Ubuntu up to 10.04 works.
  • Alpine Linux works.
• ReactOS works.
• FreeDOS, Windows 1.01 and MS-DOS run very well.
• KolibriOS works.
• Haiku works.
• Android x86 1.6-r2 works if one selects VESA mode at the boot prompt. Newer versions may work if compiled without SSE3. See #224.
• Windows 1, 3.0, 95, 98, ME and 2000 work. Other versions currently don't (see #86, #208).
  • In Windows 2000 and higher the PC type has to be changed from ACPI PC to Standard PC
• Many hobby operating systems work.
• 9front works.
• Plan 9 doesn't work.
• QNX works.
• OS/2 doesn't work.
• FreeBSD works.
• OpenBSD works with a specific boot configuration. At the boot> prompt type boot -c, then at the UKC> prompt disable mpbios and exit.
• NetBSD works only with a custom kernel, see #350.
• Older versions of SerenityOS work (1.0.gc460f4a is a known working version).

You can get some infos on the disk images here: https://github.com/copy/images.

How to build, run and embed?

You need:

• make
• Rust with the wasm32-unknown-unknown target
• A version of clang compatible with Rust
• java (for Closure Compiler, not necessary when using debug.html)
• nodejs (a recent version is required, v16.11.1 is known to be working)
• To run tests: nasm, gdb, qemu-system, gcc, libc-i386 and rustfmt

See tools/docker/test-image/Dockerfile for a full setup on Debian or WSL.

• Run make to build the debug build (at debug.html).
• Run make all to build the optimized build (at index.html).
• ROM and disk images are loaded via XHR, so if you want to try out index.html locally, make sure to serve it from a local webserver. You can use make run to serve the files using Python's http module.
• If you only want to embed v86 in a webpage you can use libv86.js. For usage, check out the examples. You can download it from the release section.

Alternatively, to build using docker

• If you have docker installed, you can run the whole system inside a container.
• See tools/docker/exec to find Dockerfile required for this.
• You can run docker build -f tools/docker/exec/Dockerfile -t v86:alpine-3.14 . from the root directory to generate docker image.
• Then you can simply run docker run -it -p 8000:8000 v86:alpine-3.14 to start the server.
• Check localhost:8000 for hosted server.

Testing

The disk images for testing are not included in this repository. You can download them directly from the website using:

wget -P images/ https://k.copy.sh/{linux.iso,linux4.iso,buildroot-bzimage.bin,openbsd-floppy.img,kolibri.img,windows101.img,os8.img,freedos722.img}

Run all tests: make jshint rustfmt kvm-unit-test nasmtests nasmtests-force-jit expect-tests jitpagingtests qemutests rust-test tests

See tests/Readme.md for more infos.

API examples

• Basic
• Programatically using the serial terminal
• A Lua interpreter
• Two instances in one window
• Saving and restoring emulator state

Using v86 for your own purposes is as easy as:

var emulator = new V86Starter({
    screen_container: document.getElementById("screen_container"),
    bios: {
        url: "../../bios/seabios.bin",
    },
    vga_bios: {
        url: "../../bios/vgabios.bin",
    },
    cdrom: {
        url: "../../images/linux.iso",
    },
    autostart: true,
});

See starter.js.

License

v86 is distributed under the terms of the Simplified BSD License, see LICENSE. The following third-party dependencies are included in the repository under their own licenses:

• lib/softfloat/softfloat.c
• lib/zstd/zstddeclib.c
• tests/kvm-unit-tests/
• tests/qemutests/

Credits

• CPU test cases via QEMU
• More tests via kvm-unit-tests
• zstd support is included for better compression of state images
• Berkeley SoftFloat is included to precisely emulate 80-bit floating point numbers
• The jor1k project for 9p, filesystem and uart drivers
• WinWorld sources of some old operating systems

More questions?

Shoot me an email to copy@copy.sh. Please report bugs on GitHub.

Author

Fabian Hemmer (https://copy.sh/, copy@copy.sh)