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Plex86/Bochs VGABios
The goal of this project is to have a LGPL'd Video Bios in plex86,
Bochs and qemu.
This VGA Bios is very specific to the emulated VGA card.
It is NOT meant to drive a physical vga card.
Cirrus SVGA extension
The Cirrus SVGA extension is designed for the Cirrus emulation in Bochs and
qemu. The initial patch for the Cirrus extension has been written by Makoto
Suzuki (suzu).
To compile the VGA Bios you will need :
- gcc
- bcc
- as86
- ld86
Untar the archive, and type make. You should get a "VGABIOS-lgpl-latest.bin"
file. Alternatively, you can use the binary file "VGABIOS-lgpl-latest.bin",
i have compiled for you.
Edit your plex86/bochs conf file, and modify the load-rom command in the
VGA BIOS section, to point to the new vgabios image file.
You can get a very basic debugging system: messages printed by the vgabios.
You have to register the "unmapped" device driver in plex86 or bochs, and make
sure it grabs port 0xfff0.
Comment the #undef DEBUG at the beginning of vgabios.c.
You can then use the "printf" function in the bios.
Look at the "testvga.c" file in the archive. This is a minimal Turbo C 2.0
source file that calls a few int10 functions. Feel free to modify it to suit
your needs.
Copyright and License
This program has been written by Christophe Bothamy
It is protected by the GNU Lesser Public License, which you should
have received a copy of along with this package.
Reverse Engineering
The VGA Bios has been written without reverse-engineering any existing Bios.
The source code contains code ripped from rombios.c of plex86, written
by Kevin Lawton <>
The source code contains fonts from (c) by Joseph Gil avalable at :
These fonts are public domain
The source code is based on information taken from :
- Kevin Lawton's vga card emulation for bochs/plex86
- Ralf Brown's interrupts list avalaible at
- Finn Thogersons' VGADOC4b available at
- Michael Abrash's Graphics Programming Black Book
- Francois Gervais' book "programmation des cartes graphiques cga-ega-vga"
edited by sybex
- DOSEMU 1.0.1 source code for several tables values and formulas
Please report any bugs, comments, patches for this VGA Bios to
You can find the latest release at :
For any information on bochs, visit the website
For any information on qemu, visit the website
vgabios-0.6c : Apr 08 2009
- Volker
. added DPMS support to cirrus vgabios (patch from Gleb Natapov)
. use VBE LFB address from PCI base address if present
. added support for a lot more non-standard VBE modes (e.g. widescreen modes)
. minor bugfixes
vgabios-0.6b : May 30 2008
- Volker
. added PCI data structure for the Cirrus VGABIOS images
. minor bugfixes in biossums utility, VBE support and makefile
vgabios-0.6a : Aug 19 2006
- Volker
. added minimal support for the video parameter table (VPT)
. Cirrus SVGA now supports the "no clear" bit in Cirrus and VESA mode
. Bochs VBE protected mode interface improved
. save/restore video state support for Bochs VBE and standard VGA added
. generate vbetables.h dynamicly
. VBE video memory increased to 8 MB (VBE dispi ID changed to B0C4)
. lots of 4bpp VBE fixes (all 4bpp VBE modes now enabled)
. VGA compatible setup for VBE modes added
vgabios-0.5d : Dec 29 2005
- Volker
. Bochs VBE protected mode interface added (based on a patch by
. biossums utility now supports VGABIOS sizes up to 64 kBytes
. VGA mode 0x11: all color planes must be enabled in this 2-color VGA mode
vgabios-0.5c : Jul 07 2005
- Volker
. BIOS configuration word usually reports initial mode 80x25 color text
. vgabios function 0x0e (write teletype): linefeed (0x0a) only increments the
cursor row value
vgabios-0.5b : May 24 2005
- Volker
. fixed return value for the default case in the VBE section (non-debug mode)
. removed unused stuff
vgabios-0.5a : Mar 07 2005
- Volker
. Cirrus SVGA extension (initial patches from Makoto Suzuki, improvements
from Fabrice Bellard)
. vgabios image size is now exactly 32k with a checksum
. a lot of vgabios and vbe functions rewritten in assembler
. dynamicly generated VBE mode info list
. write character function for CGA and LINEAR8 modes
. read/write graphics pixel for some graphics modes
. text scroll feature for some graphics modes
. VBE 8-bit DAC support
vgabios-0.4c : Nov 06 2003
- Christophe
. fix font problem on initial screen of NT4 Loader
vgabios-0.4b : Nov 04 2003
- Volker
. fix offset of character tables
. optimizations of CRT controller accesses
. VBE i/o registers changed to 0x01CE/CF
(suggestion from Daniel Gimpelevich)
. "noclear" flag stored in BIOS area
. fix character height returned by get_font_info function
vgabios-0.4a : Aug 17 2003
- Volker
. VBE mode search rewritten (VBE modes with LFB bit removed)
. many bugfixes and optimizations
. write character function implemented for graphics modes
. support for 15bpp, 16bpp, 24bpp and 32bpp VBE modes added
. SVGA mode 0x6A added
. VBE modes 0x102, 0x117, 0x118 and 0x142 (Bochs specific)
vgabios-0.3b : Nov 23 2002
- Christophe
. added lfb-mode numbers (patch from mathis)
. updated the Makefile
. removed display of copyrights.
. changed the Copyright string to "LGPL VGABios developers"
- Volker
. set the cursor shape depending on the current font height
. clear BL before calling int 0x10 function 0x1103 in vgabios_init_func
. added some text font functions
- Jeroen
. Forced to new DISPI (0xb0c1) interface (requires latest bochs vbe code)
. Added multibuffering support
. Added new DISPI interface for: virt width, height, x offset, y offset
. Added LFB modes (to be used with the vbe-lfb patch in bochs)
see VBE_HAVE_LFB in vbe.c (currently default enabled)
. updated TODO & docs for changes after bochs 1.4
vgabios-0.3a : Mar 10 2002
- Christophe
. Fixed bug in function ah=13
- Jeroen
. updated vbebios implementation to new api
. added vbe_display_api documentation
. added 640x400x8, 640x480x8, 800x600x8, 1024x768
(>640x480 needs a special bochs patch atm)
. added 320x200x8 vbe support (uses the standard 320x200x8 vga mode to
display, this allows for testing & having something on screen as well,
at least until bochs host side display is up & running)
. adding lfbprof (vbe) testprogram (+some small fixes to it)
. merging with vbebios 0.2
vgabios-0.2b : Nov 19 2001
- Christophe
. Fixed bug in function ah=13
vgabios-0.2a : Nov 09 2001
- Christophe
. Included bugfix from about grayscale summing
. Added the "IBM" string at org 0x1e as Bart Oldeman suggested
. Fixed DS and ES that where inverted in the int10 parameters list!
. The following have been implemented :
- function ax=1a00, ax=1a01, ah=1b
- function ax=1130
. Added debug messages for unimplemented/unknown functions
Must be compiled with DEBUG defined. The output is trapped
by the unknown-ioport driver of plex/bochs (port 0xfff0 is used)
vgabios-0.1a : May 8 2001
- Christophe
. First release. The work has been focused only on text mode.
. The following have been implemented :
- inits
- int 10 handler
- functions ah=00, ah=01, ah=02, ah=03, ah=05, ah=06, ah=07, ah=08
ah=09, ah=0a, ah=0e, ah=0f, ax=1000, ax=1001, ax=1002, ax=1003
ax=1007, ax=1008, ax=1009, ax=1010, ax=1012, ax=1013, ax=1015
ax=1017, ax=1018, ax=1019, ax=101a, ax=101b, ah=12 bl=10,
ah=12 bl=30, ah=12 bl=31, ah=12 bl=32, ah=12 bl=33, ah=12 bl=34