Bochs User Manual
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# bochsrc

Bochs uses a configuration file called a `bochsrc` to know where to look for disk images, how the Bochs emulation layer should work, etc. When you first start up Bochs, it looks around for its configuration file, and parses it. Here are a few lines from a sample file:

      diskc: file="30M.sample", cyl=615, heads=6, spt=17
      boot: c

The format is very strict, so be sure to put the right number of spaces and use lowercase letters. As you can see, most lines have a keyword telling what is being configured, followed by a colon, followed by a few `variable`=`value` pairs, separated by commas. For very simple options, sometimes just a single value is needed. The source and binary distributions come with a sample `bochsrc`, so you can just copy the sample file and edit the settings you need to change.

The syntax used for bochsrc can also be used as command line arguments for Bochs. If you have any spaces in your command line arguments, they should be enclosed in single quotes, for example:

      bochs 'boot:a' 'floppya: 1_44=a.img, status=inserted'

For other arguments, see section Command line arguments.

Starting with version 1.3, you can use environment variables in the bochsrc file, for example:

      diskc: file="$IMAGES/30M.sample", cyl=615, heads=6, spt=17
      boot: c

Starting with version 2.0, two environment variables have a built-in default value which is set at compile time. $BXSHARE points to the "share" directory which is typically /usr/local/share/bochs on UNIX machines. See the $(sharedir) variable in the Makefile for the exact value. $BXSHARE is used by disk images to locate the directory where the BIOS images and keymaps can be found. If $BXSHARE is not defined, Bochs will supply the default value. Also, $LTDL_LIBRARY_PATH points to a list of directories (separated by colons if more than one) to search in for Bochs plugins. A compile-time default is provided if this variable is not defined by the user. On Win32 and MacOSX, the default for the share directory is determined by a platform-specific specific algorithm. On Win32, we use the registry to see what directory Bochs and its support files were installed in. On MacOSX, the share directory is the directory where the application is located.

Starting with version 2.0, you can can use #include in the bochsrc to read the configuration from other files. Now it is possible to put platform or installation defaults in a global config file (e.g. location of rom images). Put this on top of your config file if the global configuration is stored in /etc:

     #include /etc/bochsrc

The section below lists all the supported bochsrc options.

## romimage

Examples:

      romimage: file=bios/BIOS-bochs-latest, address=0xf0000

The ROM BIOS controls what the PC does when it first powers on. Normally, you can use a precompiled BIOS in the source or binary distribution called `BIOS-bochs-latest`. The ROM BIOS is usually loaded starting at address 0xf0000, and it is exactly 64k long.

## megs

Examples:

      megs: 32
      megs: 128

Set this to the default number of megabytes of memory you want to emulate. The default is 32, since most operating systems won't need more than that.

## optromimage1, optromimage2, optromimage3 or optromimage4

Example:

       optromimage1: file=optionalrom.bin, address=0xd0000

This enables Bochs to load up to 4 optional ROM images.

Be sure to use a read-only area, typically between C8000 and EFFFF. These optional ROM images should not overwrite the rombios (located at F0000-FFFFF) and the videobios (located at C0000-C7FFF).

Those ROM images will be initialized by the bios if they contain the right signature (0x55AA).

It can also be a convenient way to upload some arbitary code/data in the simulation, that can be retrieved by the boot loader

## vgaromimage

Examples:

      vgaromimage: bios/VGABIOS-elpin-2.40
      vgaromimage: bios/VGABIOS-lgpl-latest

You also need to load a VGA ROM BIOS at 0xC0000.

A VGA BIOS file from Elpin Systems, Inc. is provided in the source and binary distributions.

A free LGPL'd VGA BIOS is also provided in the source and binary distributions.

## floppya/floppyb

Examples:

    2.88M 3.5" Floppy:
      floppya: 2_88=a:, status=inserted
    1.44M 3.5" Floppy:
      floppya: 1_44=floppya.img, status=inserted
    1.2M  5.25" Floppy:
      floppyb: 1_2=/dev/fd0, status=inserted
    720K  3.5" Floppy:
      floppya: 720k=/usr/local/bochs/images/win95.img, status=inserted

Floppya is the first drive, and floppyb is the second drive. If you're booting from a floppy, floppya should point to a bootable disk. To read from a disk image, write the name of the image file. In many operating systems Bochs can read directly from a raw floppy drive. For raw disk access, use the device name (Unix systems) or the drive letter and a colon (Windows systems). You can set the initial status of the media to `ejected` or `inserted`. Usually you will want to use `inserted`. In fact Bryce can't think of any reason to ever write `ejected` in your bochsrc.

## ata0, ata1, ata2, ata3

Examples:

    ata0: enabled=1, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
    ata1: enabled=1, ioaddr1=0x170, ioaddr2=0x370, irq=15
    ata2: enabled=1, ioaddr1=0x1e8, ioaddr2=0x3e0, irq=11
    ata3: enabled=1, ioaddr1=0x168, ioaddr2=0x360, irq=9

These options enables up to 4 ata channels. For each channel the two base io addresses and the irq must be specified. ata0 is enabled by default, with ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14

## ata0-master, ata0-slave, ata1-*, ata2-*, ata3-*

Examples:

    ata0-master: type=disk, path=10M.img, mode=flat, cylinders=306, heads=4, spt=17, translation=none
    ata1-master: type=disk, path=2GB.cow, mode=vmware3, cylinders=5242, heads=16, spt=50, translation=echs
    ata1-slave:  type=disk, path=3GB.img, mode=sparse, cylinders=6541, heads=16, spt=63, translation=auto
    ata2-master: type=disk, path=7GB.img, mode=undoable, cylinders=14563, heads=16, spt=63, translation=lba
    ata2-slave:  type=cdrom, path=iso.sample, status=inserted

This defines the type and characteristics of all attached ata devices:

Table 1. ata devices configuration options

Option | Comments | Possible values
--- | --- | ---
type | type of attached device | [disk | cdrom]
path | path of the image |
mode | image type, only valid for disks | [flat | concat | external | dll | sparse | vmware3 | undoable | growing | volatile ]
cylinders | only valid for disks |
heads | only valid for disks |
spt | only valid for disks |
status | only valid for cdroms | [inserted | ejected]
biosdetect | type of biosdetection | [none | auto], only for disks on ata0 [cmos]
translation | type of translation done by the bios (legacy int13), only for disks | [none | lba | large | rechs | auto]
model | string returned by identify device ATA command |

You have to tell the type of the attached device. For Bochs version2.0, it can by disk or cdrom

You have to point the "path" at a hard disk image file, cdrom iso file, or physical cdrom device. To create a hard disk image, try running bximage. It will help you choose the size and then suggest a line that works with it.

In UNIX it is possible to use a raw device as a Bochs hard disk, but WE DON'T RECOMMEND IT for safety reasons.

The path, cylinders, heads, and spt are mandatory for type=disk

The path is mandatory for type=cdrom

The disk translation scheme (implemented in legacy int13 bios functions, and used by older operating systems like MS-DOS), can be defined as:

- none : no translation, for disks up to 528MB (1032192 sectors)

- large : a standard bitshift algorithm, for disks up to 4.2GB (8257536 sectors)

- rechs : a revised bitshift algorithm, using a 15 heads fake physical geometry, for disks up to 7.9GB (15482880 sectors). (don't use this unless you understand what you're doing)

- lba : a standard lba-assisted algorithm, for disks up to 8.4GB (16450560 sectors)

- auto : autoselection of best translation scheme. (it should be changed if system does not boot)

Please see the Section called Disk translation in the chapter called Tips and Techniques for a discussion on translation scheme.

The mode option defines how the disk image is handled. Disks can be defined as:

- flat : one file flat layout

- concat : multiple files layout

- external : developer's specific, through a C++ class

- dll : developer's specific, through a DLL

- sparse : stackable, commitable, rollbackable

- vmware3 : vmware3 disk support

- undoable : flat file with commitable redolog

- growing : growing file

- volatile : flat file with volatile redolog

Please see the Section called Disk Image Modes in the chapter called Tips and Techniques for a discussion on disk modes.

Default values are:

       mode=flat, biosdetect=auto, translation=auto, model="Generic 1234"

The biosdetect option has currently no effect on the bios

## newharddrivesupport

Examples:

      newharddrivesupport: enabled=1

This setting enables support for large hard disks, better CD recognition, and various other useful functions. You can set it to "enabled=1" (on) or "enabled=0" (off). It is recommended that this setting is left on unless you are having trouble with it.

## boot

Examples:

      boot: floppy
      boot: disk
      boot: cdrom

This defines your boot drive. You can either boot from 'floppy', 'disk' or 'cdrom'. 'c' and 'a' are also accepted for historical reasons.

## floppy_bootsig_check

Example:

      floppy_bootsig_check: disabled=1

This disables the 0xaa55 signature check on boot floppies The check is enabled by default.

## config_interface

The configuration interface is a series of menus or dialog boxes that allows you to edit all the settings that control Bochs's behavior. There are two choices of configuration interface: a text mode version called "textconfig" and a graphical version called "wx". The text mode version uses stdin/stdout and is always available. The graphical version is only compiled when you use "--with-wx" in the configure command. If you do not write a config_interface line, Bochs will choose a default for you (usually textconfig).

| wxWindows provides both a configuration interface and a display library. So if you use the "wx" configuration interface, you must also use the "wx" display library.

Examples:

      config_interface: textconfig
      config_interface: wx

## display_library

The display library is the code that displays the Bochs VGA screen. Bochs has a selection of about 10 different display library implementations for different platforms. If you run configure with multiple --with-* options, the display_library command lets you choose which one you want to run with. If you do not write a display_library line, Bochs will choose a default for you.

Table 2. display_library values

Option | Description
--- | ---
x | use X windows interface, cross platform
win32 | use native win32 libraries
carbon | use Carbon library (for MacOS X)
beos | use native BeOS libraries
macintosh | use MacOS pre-10
amigaos | use native AmigaOS libraries
sdl | use SDL library, cross platform
svga | use SVGALIB library for Linux, allows graphics without X windows
term | text only, uses curses/ncurses library, cross platform
rfb | provides an interface to AT&T's VNC viewer, cross platform
wx | use wxWindows library, cross platform
nogui | no display at all

Examples:

      display_library: x
      display_library: sdl

| wxWindows provides both a configuration interface and a display library. So if you use the "wx" configuration interface, you must also use the "wx" display library.

## log

Examples:

      log: bochsout.txt
      log: /dev/tty               (unix only)
      log: /dev/null              (unix only)

Give the path of the log file you'd like Bochs debug and misc. verbage to be written to. If you really don't want it, make it /dev/null.

## logprefix

Examples:

       logprefix: %t-%e-@%i-%d
       logprefix: %i%e%d

This handles the format of the string prepended to each log line. You may use those special tokens :

      %t : 11 decimal digits timer tick
      %i : 8 hexadecimal digits of cpu0 current eip
      %e : 1 character event type ('i'nfo, 'd'ebug, 'p'anic, 'e'rror)
      %d : 5 characters string of the device, between brackets

Default is %t%e%d

## debug/info/error/panic

Examples:

      debug: action=ignore
      info: action=report
      error: action=report
      panic: action=ask

During simulation, Bochs encounters certain events that the user might want to know about. These events are divided into four levels of importance: debug, info, error, and panic. Debug messages are usually only useful when writing Bochs code or when trying to locate a problem. There may be thousands of debug messages per second, so be careful before turning them on. Info messages tell about interesting events that don't happen that frequently. Bochs produces an "error" message when it finds a condition that really shouldn't happen, but doesn't endanger the simulation. An example of an error might be if the emulated software produces an illegal disk command. Panic messages mean that Bochs cannot simulate correctly and should probably shut down. A panic can be a configuration problem (like a misspelled bochsrc line) or an emulation problem (like an unsupported video mode).

The debug, info, error, and panic lines in the bochsrc control what Bochs will do when it encounters each type of event. The allowed actions are: fatal (terminate bochs), ask (ask the user what to do), report (print information to the console or log file), or ignore (do nothing). The recommended settings are listed in the sample above.

The safest action for panics is "fatal" or "ask". If you are getting lots of panics and get tired of telling it to continue each time, you can try action=report instead. If you allow Bochs to continue after a panic, don't be surprised if you get strange behavior or crashes after a panic occurs. Please report panic messages to the bochs-developers mailing list unless it is just a configuration problem like "could not find hard drive image."

## debugger_log

Examples:

      log: debugger.out
      log: /dev/null              (unix only)
      log: -

Give the path of the log file you'd like Bochs to log debugger output. If you really don't want it, make it '/dev/null', or '-'.

## com1

Specifies the device to use as com1. This can be a real serial line, or a pty. To use a pty (under X/Unix), create two windows (xterms, usually). One of them will run bochs, and the other will act as com1. Find out the tty the com1 window using the `tty' command, and use that as the `dev' parameter. Then do `sleep 1000000' in the com1 window to keep the shell from messing with things, and run bochs in the other window. Serial I/O to com1 (port 0x3f8) will all go to the other window.

Examples:

    com1: dev=/dev/ttyp9
    com1: dev=/dev/cua0

## parport1

This defines a parallel (printer) port. When turned on and an output file is defined emulated printer port sends characters printed by the guest OS into the output file. On some platforms a device filename can be used to send the data to the real parallel port (e.g. "/dev/lp0" on Linux, "lpt1" on win32 platforms).

Examples:

    parport1: enabled=1, file="parport.out"
    parport1: enabled=1, file="/dev/lp0"
    parport1: enabled=0

## sb16

Examples:

      sb16: midimode=1, midi=/dev/midi00, wavemode=1, wave=/dev/dsp,
            loglevel=2, log=sb16.log, dmatimer=600000

| The example is wrapped onto several lines for formatting reasons, but it should all be on one line in the actual bochsrc file.

The sb16 line defines Sound Blaster 16 emulation. It can have several of the following properties. All properties are in the usual "property=value" format.

- midi: The filename is where the midi data is sent. This can be a device or just a file if you want to record the midi data.

- midimode:

         0 = No data should be output.
         1 = output to device (system dependent - midi denotes the device driver).
         2 = SMF file output, including headers.
         3 = Output the midi data stream to the file (no midi headers and no
             delta times, just command and data bytes).

- wave: This is the device/file where wave output is stored.

- wavemode:

         0 = no data
         1 = output to device (system dependent - wave denotes the device driver).
         2 = VOC file output, including headers.
         3 = Output the raw wave stream to the file.

- log: The file to write the sb16 emulator messages to.

- loglevel:

         0 = No log.
         1 = Only midi program and bank changes.
         2 = Severe errors.
         3 = All errors.
         4 = All errors plus all port accesses.
         5 = All errors and port accesses plus a lot of extra information.

- dmatimer: Microseconds per second for a DMA cycle. Make it smaller to fix non-continuous sound. 750000 is usually a good value. This needs a reasonably correct setting for IPS (see below).

## vga_update_interval

Examples:

      vga_update_interval: 250000

Video memory is scanned for updates and screen updated every so many virtual seconds. The default is 300000, about 3Hz. This is generally plenty. Keep in mind that you must tweak the 'ips:' directive to be as close to the number of emulated instructions-per-second your workstation can do, for this to be accurate.

## keyboard_serial_delay

Example:

      keyboard_serial_delay: 200

Approximate time in microseconds that it takes one character to be transfered from the keyboard to controller over the serial path.

## keyboard_paste_delay

Example:

      keyboard_paste_delay: 100000

Approximate time in microseconds between attempts to paste characters to the keyboard controller. This leaves time for the guest os to deal with the flow of characters. The ideal setting depends on how your operating system processes characters. The default of 100000 usec (.1 seconds) was chosen because it works consistently in Windows.

## floppy_command_delay

Examples:

      floppy_command_delay: 50000

Time in microseconds to wait before completing some floppy commands such as read, write, seek, etc., which normally have a delay associated. This was once hardwired to 50000 but now you can adjust it.

## ips

Examples:

      ips: 1000000

Emulated Instructions Per Second. This is the number of IPS that bochs is capable of running on your machine. You can recompile Bochs, using instructions included in config.h (in the source code), to find your workstation's capability.

IPS is used to calibrate many time-dependent events within the bochs simulation. For example, changing IPS affects the frequency of VGA updates, the duration of time before a key starts to autorepeat, and the measurement of BogoMips and other benchmarks. The table below lists some typical IPS settings for different machines[1].

Table 3. Example IPS Settings

Speed | Machine | Typical IPS
--- | --- | ---
650Mhz | Athlon K-7 with Linux 2.4.x | 2 to 2.5 million
400Mhz | Pentium II with Linux 2.0.x | 1 to 1.8 million
166Mhz | 64bit Sparc with Solaris 2.x | 0.75 million
200Mhz | Pentium with Linux 2.x | 0.5 million

## clock

This defines the parameters of the clock inside Bochs:

sync

TO BE COMPLETED (see Greg explaination in bug #536329)

time0

Specifies the start (boot) time of the virtual machine. Use a time value as returned by the time(2) system call. If no time0 value is set or if time0 equal to 1 (special case) or if time0 equal 'local', the simulation will be started at the current local host time. If time0 equal to 2 (special case) or if time0 equal 'utc', the simulation will be started at the current utc time.

    Syntax:
      clock: sync=[none|slowdown|realtime], time0=[timeValue|local|utc]

    Examples:
      clock: sync=none,     time0=local       # Now (localtime)
      clock: sync=slowdown, time0=315529200   # Tue Jan  1 00:00:00 1980
      clock: sync=none,     time0=631148400   # Mon Jan  1 00:00:00 1990
      clock: sync=realtime, time0=938581955   # Wed Sep 29 07:12:35 1999
      clock: sync=realtime, time0=946681200   # Sat Jan  1 00:00:00 2000
      clock: sync=none,     time0=1           # Now (localtime)
      clock: sync=none,     time0=utc         # Now (utc/gmt)

    Default value are sync=none, time0=local

## mouse

Examples:

      mouse: enabled=1
      mouse: enabled=0

This option prevents Bochs from creating mouse "events" unless a mouse is enabled. The hardware emulation itself is not disabled by this. You can turn the mouse on by setting enabled to 1, or turn it off by setting enabled to 0. Unless you have a particular reason for enabling the mouse by default, it is recommended that you leave it off. You can also toggle the mouse usage at runtime (middle mouse button on X11 and SDL, F12 on Win32).

## private_colormap

Examples:

      private_colormap: enabled=1

Requests that the GUI create and use its own non-shared colormap. This colormap will be used when in the bochs window. If not enabled, a shared colormap scheme may be used. Once again, enabled=1 turns on this feature and 0 turns it off.

## i440fxsupport

Examples:

      i440fxsupport: enabled=1

Enables limited i440fx PCI chipset support.

## usb1

Examples:

      usb1: enabled=1, ioaddr=0xFF80, irq=10

Enables the i440fx PCI USB root hub. PCI support must be enabled, too.

## ne2k

The ne2k line configures an emulated NE2000-compatible Ethernet adapter, which allows the guest machine to communicate on the network. To disable the NE2000 just comment out the ne2k line.

Examples:

    ne2k: ioaddr=0x240, irq=9, mac=b0:c4:20:00:00:00, ethmod=fbsd, ethdev=xl0
    ne2k: ioaddr=0x240, irq=9, mac=b0:c4:20:00:00:00, ethmod=fbsd, ethdev=en0 #macosx
    ne2k: ioaddr=0x240, irq=9, mac=b0:c4:20:00:00:00, ethmod=linux, ethdev=eth0
    ne2k: ioaddr=0x240, irq=9, mac=b0:c4:20:00:00:01, ethmod=win32, ethdev=MYCARD
    ne2k: ioaddr=0x240, irq=9, mac=fe:fd:00:00:00:01, ethmod=tap, ethdev=tap0
    ne2k: ioaddr=0x240, irq=9, mac=fe:fd:00:00:00:01, ethmod=tuntap, ethdev=tun0, script=./tunconfig

    ioaddr, irc: You probably won't need to change ioaddr and irq, unless there
    are IRQ conflicts.

    mac: The MAC address MUST NOT match the address of any machine on the net.
    Also, the first byte must be an even number (bit 0 set means a multicast
    address), and you cannot use ff:ff:ff:ff:ff:ff because that's the broadcast
    address.  For the ethertap module, you must use fe:fd:00:00:00:01.  There may
    be other restrictions too.  To be safe, just use the b0:c4... address.

    ethmod: The ethmod value defines which low level OS specific module to be
    used to access pysical ethernet interface. Current implemented values include :
     - fbsd : ethernet on freebsd and openbsd
     - linux : ethernet on linux
     - win32 : ethernet on win32
     - tap : ethernet through a linux tap interface
     - tuntap : ethernet through a linux tuntap interface

    ethdev: The ethdev value is the name of the network interface on your host
    platform.  On UNIX machines, you can get the name by running ifconfig.  On
    Windows machines, you must run niclist to get the name of the ethdev.
    Niclist source code is in misc/niclist.c and it is included in Windows
    binary releases.

    script: The script value is optionnal, and is the name of a script that
    is executed after bochs initialize the network interface. You can use
    this script to configure this network interface, or enable masquerading.
    This is mainly useful for the tun/tap devices that only exist during
    Bochs execution. The network interface name is supplied to the script
    as first parameter

## keyboard_mapping

Examples:

      keyboard_mapping: enabled=0, map=
      keyboard_mapping: enabled=1, map=gui/keymaps/x11-pc-de.map

This enables a remap of a physical localized keyboard to a virtualized U.S. keyboard, as the PC architecture expects. If enabled, the keymap file must be specified. Keyboard mapping is available for X windows, SDL (Linux port) and wxWindows (GTK port). For SDL you have to use keymaps designed for SDL, the wxWindows gui uses the keymaps for X windows.

## keyboard_type

Examples:

      keyboard_type: xt
      keyboard_type: at
      keyboard_type: mf

Type of keyboard returned by a "identify keyboard" command to the keyboard controller. It must be one of "xt", "at" or "mf". Defaults to "mf". It should be ok for almost everybody. A known exception is French macs, that do have a "at"-like keyboard.

## user_shortcut

Examples:

      user_shortcut: keys=ctrlaltdel
      user_shortcut: keys=ctrlaltesc

This defines the keyboard shortcut to be sent when you press the "user" button in the headerbar. The shortcut string can be a combination of these key names: "alt", "bksp", "ctrl", "del", "esc", "f1", "f4", "tab", "win". Up to 3 keys can be pressed at a time.

## cmosimage

Example:

      cmosimage: cmos.img

This defines image file that can be loaded into the CMOS RAM at startup.

## diskc/diskd

The diskc and diskd options are deprecated. Use "ataX-*: type=disk,..." options instead.

Examples:

      diskc: file=10M.img, cyl=306, heads=4, spt=17
      diskc: file=112M.img, cyl=900, heads=15, spt=17
      diskd: file=483.img, cyl=1024, heads=15, spt=63

The diskc/diskd lines tell Bochs what disk image file to use as the constants of the emulated hard drive, and what geometry it should have. Diskc is the first hard drive, and diskd is the second hard drive. Using a raw hard drive is possible under on unix but WE DON'T RECOMMEND IT for safety reasons. The file should be a disk image file, which must be exactly 512*cyl*heads*spt bytes long. The geometry settings are cylinder (cyl), heads, and sectors per track (spt). If you use bximage to create the image, it will give you the required cyl, head, and spt information.

| You cannot use both diskd and cdromd together.

## cdromd

The cdromd option is deprecated. Use "ataX-*: type=cdrom,..." option instead.

Examples:

      cdromd: dev=/dev/cdrom, status=inserted         (Unix only)
      cdromd: dev=e:, status=inserted                 (Windows only)
      cdromd: dev=cdromimage.iso, status=inserted

The cdromd line tells Bochs to emulate a CD-ROM device. You cannot have both a diskd and a cdromd, and there is no cdromc option.

| You cannot use both diskd and cdromd together.

## pit

The pit option is deprecated. Use the "clock" option instead.

Examples:

      pit: realtime=0
      pit: realtime=1

The PIT is the programmable interval timer. Bochs's PIT model was written by Greg Alexander. It has a real-time option that tries to keep the PIT in sync with the host time. This feature is still experimental, but it may be useful if you want to prevent Bochs from running too fast, for example a DOS video game. Be aware that with the realtime pit option, your simulation will not be repeatable; this can a problem if you are debugging.

## time0

The time0 option is deprecated. Use the "clock" option instead.

Examples:

      time0: 938581955

Specifies the start (boot) time of the virtual machine. Use a time value as returned by the time(2) system call. Time equal to 1 is a special case which starts the virtual machine at the current time of the simulator host.

### Notes

[1] | IPS measurements depend on OS and compiler configuration in addition to processor clock speed.

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