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Constructor for emulator instances.

Usage: var emulator = new V86Starter(options);

Options can have the following properties (all optional, default in parenthesis):

  • memory_size number (16 * 1024 * 1024) - The memory size in bytes, should be a power of 2.

  • vga_memory_size number (8 * 1024 * 1024) - VGA memory size in bytes.

  • autostart boolean (false) - If emulation should be started when emulator is ready.

  • disable_keyboard boolean (false) - If the keyboard should be disabled.

  • disable_mouse boolean (false) - If the mouse should be disabled.

  • network_relay_url string (No network card) - The url of a server running websockproxy. See Setting this will enable an emulated network card.

  • bios Object (No bios) - Either a url pointing to a bios or an ArrayBuffer, see below.

  • vga_bios Object (No VGA bios) - VGA bios, see below.

  • hda Object (No hard drive) - First hard disk, see below.

  • fda Object (No floppy disk) - First floppy disk, see below.

  • cdrom Object (No CD) - See below.

  • initial_state Object (Normal boot) - An initial state to load, see restore_state and below.

  • filesystem Object (No 9p filesystem) - A 9p filesystem, see

  • serial_container HTMLTextAreaElement (No serial terminal) - A textarea that will receive and send data to the emulated serial terminal. Alternatively the serial terminal can also be accessed programatically, see serial.html.

  • screen_container HTMLElement (No screen) - An HTMLElement. This should have a certain structure, see basic.html.

There are two ways to load images (bios, vga_bios, cdrom, hda, ...):

  • Pass an object that has a url. Optionally, async: true and size: size_in_bytes can be added to the object, so that sectors of the image are loaded on demand instead of being loaded before boot (slower, but strongly recommended for big files). In that case, the Range: bytes=... header must be supported on the server. Note: the python SimpleHTTPServer does not support this, so it won't work with the default webserver used by make run.

    // download file before boot
    bios: { 
        url: "bios/seabios.bin" 
    // download file sectors as requested, size is required
    hda: { 
        url: "disk/linux.iso",
        async: true,
        size: 16 * 1024 * 1024 
  • Pass an ArrayBuffer or File object as buffer property.

    // use <input type=file>
    bios: { 
        buffer: document.all.hd_image.files[0]
    // start with empty hard drive
    hda: { 
        buffer: new ArrayBuffer(16 * 1024 * 1024)


  1. Object options – Options to initialize the emulator with.


Start emulation. Do nothing if emulator is running already. Can be asynchronous.


Stop emulation. Do nothing if emulator is not running. Can be asynchronous.


Restart (force a reboot).

add_listener(string event, function(*) listener)

Add an event listener (the emulator is an event emitter). A list of events can be found at

The callback function gets a single argument which depends on the event.


  1. string event – Name of the event.
  2. function(*) listener – The callback function.

remove_listener(string event, function(*) listener)

Remove an event listener.


  1. string event
  2. function(*) listener

restore_state(ArrayBuffer state)

Restore the emulator state from the given state, which must be an ArrayBuffer returned by save_state.

Note that the state can only be restored correctly if this constructor has been created with the same options as the original instance (e.g., same disk images, memory size, etc.).

Different versions of the emulator might use a different format for the state buffer.


  1. ArrayBuffer state

save_state(function(Object, ArrayBuffer) callback)

Asynchronously save the current state of the emulator. The first argument to the callback is an Error object if something went wrong and is null otherwise.


  1. function(Object, ArrayBuffer) callback

get_statistics() -> Object

Deprecated - Might be removed in a later release.

Return an object with several statistics. Return value looks similar to (but can be subject to change in future versions or different configurations, so use defensively):

    "cpu": {
        "instruction_counter": 2821610069
    "hda": {
        "sectors_read": 95240,
        "sectors_written": 952,
        "bytes_read": 48762880,
        "bytes_written": 487424,
        "loading": false
    "cdrom": {
        "sectors_read": 0,
        "sectors_written": 0,
        "bytes_read": 0,
        "bytes_written": 0,
        "loading": false
    "mouse": {
        "enabled": true
    "vga": {
        "is_graphical": true,
        "res_x": 800,
        "res_y": 600,
        "bpp": 32


  • Object

is_running() -> boolean


  • boolean

keyboard_send_scancodes(Array.<number> codes)

Send a sequence of scan codes to the emulated PS2 controller. A list of codes can be found at Do nothing if there is no keyboard controller.


  1. Array.<number> codes

mouse_set_status(boolean enabled)

Enable or disable sending mouse events to the emulated PS2 controller.


  1. boolean enabled

keyboard_set_status(boolean enabled)

Enable or disable sending keyboard events to the emulated PS2 controller.


  1. boolean enabled

serial0_send(string data)

Send a string to the first emulated serial terminal.


  1. string data

create_file(string file, Uint8Array data, function(Object) callback)

Write to a file in the 9p filesystem. Nothing happens if no filesystem has been initialized. First argument to the callback is an error object if something went wrong and null otherwise.


  1. string file
  2. Uint8Array data
  3. function(Object) (optional) callback

read_file(string file, function(Object, Uint8Array) callback)

Read a file in the 9p filesystem. Nothing happens if no filesystem has been initialized.


  1. string file
  2. function(Object, Uint8Array) callback