Starting with 1.47, changes marked with SYSLINUX, PXELINUX, ISOLINUX
or EXTLINUX apply to that specific program only; other changes apply
to all derivatives.
Changes in 3.82:
* isohybrid: fix the -partok logic for loading from a partition.
* ISOLINUX: deal with systems which return from INT 13h with
* Do not invoke the idle handler during large file loads.
* Simple menu: make ONTIMEOUT work with MENU HIDDEN.
Changes in 3.81:
* Shuffler: fix bug in real-mode entry. This affected a
number of modules, probably in relatively unimportant ways,
but it completely broke linux.c32.
* Improved performance.
* Attempt to halt the processor while idle. This can cause
bad reponsiveness when using a serial console especially for
automated input; if that ends up being a problem, use the
new "NOHALT 1" configuration command.
* linux.c32 now suppresses all messages if the "quiet" flag is
* isohybrid: add a variety of options, and a help message.
* ISOLINUX: fix booting in hybrid mode when CBIOS is used.
This unfortunately means that the isohybrid handoff protocol
has changed, so the isohybrid utility must version-match
* Drop support for ACPI 3 extended memory flags.
* Menu system: don't set the autocr flag on the serial
* altmbr: fix handling of logical partitions.
* altmbr: cap at 439 bytes so the partition select byte isn't
part of the file.
Changes in 3.80:
* New shuffler mechanism and API.
* Rewritten mboot.c32 module.
* The syslinux_boot_linux() function has been simplified.
* Don't hang trying to boot a "menu quit" label from the CLI.
* Fix problem with boot-once "sticking" on some BIOSes.
* isohybrid: fix problem with images over 2 GB in size.
* APM poweroff module (poweroff.com) by Sebastian Herbszt.
* ISOLINUX: fix the handling of large directories. Bug found
and fixed by Steffen Winterfeldt.
Changes in 3.75:
* PXELINUX: fix the "keeppxe" option, which was broken in
* MEMDISK: correct the extraction of geometry information from
the MBR of a hard disk image, again broken in 3.74.
* extlinux(1) man page from Brian Pellin.
* Simple menu: MENU SAVE is now controllable on a menu-by-menu
or entry-by-entry basis.
* gPXELINUX: fix interrupt-disabling bug.
* HDT: fix lockup on machines with certain PCI configurations.
Changes in 3.74:
* New UI directive, which allows a more natural way to specify
a menu system (or not.) With the UI directive specifying
the menu system, the DEFAULT directive can be used to select
the default entry inside the menus.
* kbdmap.c32: new module to load a new keyboard map
* isohybrid: workaround bug in some versions of binutils.
* Fix issue with the placement of the initrd on some machines.
* ifcpu64: fix handling of less than three arguments.
* Fix bug in the shuffle library when dealing with a very
large number of fragments.
* Documentation fixes by Vicente Jimenez Aguilar.
* gPXE updated to version 0.9.7.
* hdt.c32: Hardware Detection Tool, an interactive hardware
analyzer module by Erwan Velu.
* MEMDISK: enable automatic determination of the disk geometry
for a large floppy disk image if (and only if) it is
formatted with a FAT filesystem.
* SYSLINUX: fix the handling of .bss files on FAT12/16.
* Suppress the Loading ... message if "quiet" is specified on
the kernel command line.
* Fix the use of "CONSOLE 0" with menu.c32.
* Allow COM32 modules to be aware of all memory even in the
presence of a memory hole. The "linux.c32" module can be
used to load a kernel (or memdisk) plus large initrd on
such a system.
* MBR: produce alternate MBR variants which force the drive
number to hd0 (_f variants), or force the drive number to
hd0 if the Ctrl key is pressed (_c variants.) Furthermore,
add an MBR variant (altmbr*.bin) which ignores the active
flag and instead boots the partition number specified in the
byte at offset 439 decimal.
* Add IPAPPEND strings to com32 modules, especially needed for
* New MENU SAVE directive which saves the latest menu
selection until the next boot. Currently only implemented for
* gfxboot.com: *experimental* interface module to Steffen
Winterfeldt's "gfxboot" graphical front end
(http://gfxboot.sourceforge.net/). Module by Sebastian Herbszt.
Changes in 3.73:
* Upgrade gPXE to release version 0.9.5.
* Fix a number of build errors on various platforms.
* Handle systems with E820 "extended attributes" per ACPI 3.
Someone "cleverly" decided to change the E820 spec in a
* MEMDISK: default to "safeint".
* Adopt the moniker "The Syslinux Project", standard proper
noun capitalization, to refer to the project as a whole.
Thus, reserve the all-caps "SYSLINUX" to refer to the FAT
* mboot.c32: add "-solaris" option to pass DHCP information to
the Solaris kernel; required for automatic Solaris boot
without using Solaris' pxeboot program.
* config.c32: trivial COM32 module to restart Syslinux with
another configuration file from the command line (equivalent
to the CONFIG command in the configuratin file.)
Changes in 3.72:
* Include the pxechain.com module from Jeffery Hutzelman at
Carnegie Mellon University. This allows chaining another
PXE boot program while changing the DHCP packet passed to
* Reorganize the Makefile system.
* Major PCI core cleanups and other source cleanup.
* gPXE code updated.
* Try to avoid memory-snooping attacks on passwords. Note
that if someone has root on the box, they generally don't
need to compromise the boot loader...
* ISOLINUX: fix crash when given a zero-length file.
* sdi.c32: support gzipped SDI images.
* ISOLINUX: support generating images which can be either
a CD-ROM or a hard disk (USB disk, etc.) See
doc/isolinux.txt for more information.
* Remote gdb support for COM32 modules; patch from Stefan
* Support beeps in F-key help in the simple menu system.
* Tab display of labels, based on a patch from Sebastian
Herbszt. Can be disabled with the NOCOMPLETE configuration
* "menu default" can now be specified after "menu begin", to
indicate that a specific submenu should be the default entry.
Changes in 3.71:
* Workaround for a VESA BIOS which tries to make DOS system
* Simple menu: fix navigation around disabled entries
(or at least try to...)
* EXTLINUX: proper error message when confused about mount
* MEMDISK: be smarter about incompletely disabled floppies in
the BIOS and about being the only floppy.
* Optionally allow initrd to be specified on a separate line
rather than as part of the "append" line. This is not
recommended, but apparently makes life easier for some
* SYSLINUX: if no config file is present, set the current
directory to the root directory (Sebastian Herbszt).
* chain.c32: option "hide" to support hiding and unhiding of
primary partitions on the boot drive with DOS, Win, or OS/2
partition types (01, 04, 06, 07, 0b, 0c, 0e).
* Unbreak the KBDMAP command (broken in 3.70).
* EXTLINUX: fix the handling of the ADV when using CBIOS.
* ifcpu64.c32: simple COM32 module to select a 32- or 64-bit
kernel (and optionally 32-bit kernels with or without PAE.)
Eventually we want a scripting language for this
kind of stuff; a Lua module is under development.
* Fix parsing of the SERIAL command without a baud rate
* chain.c32: error out when try to boot an unbootable
* SYSLINUX: when building the Win32 installer, search for
MinGW under a large number of possible names.
Changes in 3.70:
* PXELINUX: Support enhanced capabilities when running on top
of gPXE (http://www.etherboot.org/). In particular, support
URL-style syntax for filenames, and any protocol that gPXE
supports (except, currently, iSCSI and AoE.) This feature
is currently highly experimental.
* Substantial infrastructure changes to support files whose
length aren't known at open time (typically network
connections.) Please note that the semantics of some of the
comboot APIs have changed slightly; please see doc/comboot.txt.
* PXELINUX: We no longer require a TFTP server which supports
the tsize option for all transfers.
* PXELINUX: Integrate with the gPXE source base; unified image
now included as "gpxelinux.0".
* The source tree has been restructured; files that were
previously in the root have moved into the core, dos, gpxe,
and utils directories.
* "make install", "make netinstall", and "make extbootinstall"
have been updated massively. "make install-all" now installs
* Change default dir for auxiliary files from
/usr/lib/syslinux to /usr/share/syslinux.
* SYSLINUX: VFAT long filename support.
* MEMDISK: Any image less than 4096K (4 MB) is treated as a
floppy disk. The geometry-guessing code will recognize all
common extended formats, but it is still possible some very
exotic formats need geometry specification. Large floppies
and very small harddisks still need explicit specification.
* chain.c32: option "swap" to support swapping of BIOS drive
numbers. This is necessary to boot certain operating systems
(DOS, Windows) from a secondary drive.
* chain.c32: option "file=" to support loading a boot file from
the SYSLINUX filesystem instead of loading the boot sector
from the drive.
* chain.c32: option "seg=" to control the load location.
* chain.c32: option "ntldr=" as a shorthand for "seg=0x2000
file="; use this to load one of WinNT's loaders:
chain.c32 hd0 1 ntldr=/MiniNT/setupldr.bin
Note that the file needs to be in the SYSLINUX filesystem.
* chain.32: options "freedos=" and "msdos="/"pcdos=" as
shorthands for "seg=0x60 file=" and "seg=0x70 file="
respectively; use this to load FreeDOS's kernel.sys, MS-DOS's
io.sys or PC-DOS's ibmbio.sys.
* Change to the A20 algorithm which *MIGHT* help systems that
have systems which freeze when Syslinux is used with USB
keyboards. Note that this has been hard do verify, so I
would greatly appreciate feedback on it.
* Complex menu system: unbreak menus which has unnamed
submenus, like complex.c.
* Fix newline on the serial port for some com32 modules.
* chain.c32: support "boot" as the drive specification,
indicating the drive from which it was booted
* SYSLINUX/EXTLINUX: support "localboot" with the same feature
set as ISOLINUX.
* Add an experimental MBR for GPT partition tables.
* Use $(CC) when determining compile flags.
* chain.c32: fix booting from logical partitions (Sergey
Changes in 3.63:
* Fix errors in the PCI and DMI detection modules (Erwan Velu,
* Fix host dependencies and other issues in the build system.
* PXELINUX: Allow class E addresses as unicast.
* sdi.c32: module to load Microsoft System Deployment Images.
For additional information, please see:
* EXTLINUX: Correct reading directories with deleted entries.
* Shuffle library: correct the handling of certain geometries
(an upward move with source material blocking the move); as
required by sdi.c32 but theoretically possible for other
formats as well.
* Add "make netinstall" to install /tftpboot.
* Fix some documentation files that didn't get moved/renamed.
Changes in 3.62:
* Clean up garbage after "aborted." message.
* Clean up memdump.com filenames.
* Support SHA256 and SHA512 encrypted passwords.
* The shuffle library now can generate chained descriptors,
thus allowing pretty much arbitrarily complex memory maps.
* Handle command lines up to 2047 characters, the current
Linux kernel limit.
* vesamenu: support systems without linear framebuffer support
(sigh, what is this, 1993?) and 15-bit RGB modes.
* Move the label storage (for the command-line interface) to
high memory, removing the size limit and freeing up 64K of
* Get rid of 4096-entry limit in the simple menu system.
* New hierarchial submenu support: see MENU BEGIN, MENU END,
MENU GOTO in doc/menu.txt.
* MENU QUIT allows creating a menu entry for returning to the
* ISOLINUX: Work around bug in certain Adaptec BIOSes,
patch by Bruce Robson.
* pngtopnm dependency removed from samples/ directory.
* Text documentation files (in doc/) renamed *.doc -> *.txt.
Changes in 3.61:
* EXTLINUX: fix crash when accessing an empty file.
* elf.c32: If a PHDR segment is present, load it.
* Fix SHA-1 and MD5 passwords.
* ISOLINUX: fix booting when mastered without
mkisofs -boot-info-table (broken since 3.50, sigh...)
* Handle BIOSes which emit multiple contiguous valid
memory regions in the e820 map.
Changes in 3.60:
* Support for "auxilliary data vector", a small amount of
writable storage. Currently only supported for EXTLINUX,
but the infrastructure is there for the other derivatives,
assuming a suitable storage location can be found.
* EXTLINUX: boot-once support (--once, --clear-once, and
* A command is now required to the EXTLINUX installer, i.e. at
least one of --install, --update, --once, --clear-once, or
Changes in 3.55:
* PXELINUX: as per RFC 5071, PXELINUX no longer requires the
use of the magic cookie option (208) for unencapsulated
options. Currently it does not require it for
vendor-encapsulated options (vendor-option-space) either,
but that MAY be reverted in the future if it causes
* Documentation text files moved to a common "doc" directory;
man pages from the Debian project added to the "man"
* Correct bug with self-overlapping memory areas when using
the shuffle interface.
Changes in 3.54:
* Add "menu separator", "menu indent", "menu disabled"
* vesamenu: fix handing of VESA modes with noncontiguous
memory buffers. In particular, Qemu/KVM sets up such a mode
when Cirrus Logic emulation is enabled (which is the
* Support for calling real mode functions using far calls,
with argument on the stack. This was implemented to support
the BIOS BBS specification, but subsequent experiments show
that the at least one of the most common BIOS cores, Award,
passes the presence check but doesn't actually implement the
Changes in 3.53:
* Fix bugs related to the $PnP BIOS functionality on some
* PXELINUX: Fix the "naked" version of :: (suppress prefix.)
* elf.c32: better error messages.
* Faster operation under Intel VT virtualization.
* PXELINUX: Fix DHCP bootfile option.
* mkdiskimage: Support more than 1024 cylinders.
* (Hopefully) fix installer on non-x86 platforms.
* Fix shuffle_and_boot_rm, used by linux.c32.
* Fix shuffle_and_boot_pm on 386/486.
* ISOLINUX (at least): fix bss memory overwrite hang.
* MBR: Fix booting from logical partitions.
* Code cleanups.
Changes in 3.52:
* Handle capitalized F-key commands in the menu system.
* Fix padding error when loading multiple ramdisks.
* Workaround for VMware crashing when trying to print a
message during early kernel boot (does not seem to work,
* chain.c32: add the ability to search for a specific MBR
signature at runtime.
* Fall back to the server identity option if the siaddr field
in the DHCP header isn't set. This seems to match the
behaviour of most PXE stacks.
* mkdiskimage: give the generated disk image an MBR signature.
* MEMDISK: Fix failures on some BIOSes.
* Simple menu system: new "MENU HIDDEN" option to not display
the menu unless the user presses a key.
* Simple menu system: support MD5-encrypted passwords (modern
Unix standard style, with "$1$" prefixes.)
* pcitest.c32: now functions as a full "lspci". Thanks to
Erwan Velu for this work.
* MEMDISK: Make EDD actually work.
* ISOLINUX: Fix for certain broken CD-ROM BIOSes which
randomly corrupted register FS.
* Simple menu system: fix memory overwrite bug that caused
some systems to lock up or behave weirdly.
* Fix building on 64-bit systems without a 32-bit libc installed.
Changes in 3.51:
* EXTLINUX: Fix failure to find the configuration file.
Changes in 3.50:
* New keywords allow the type of file to be specified in the
* It is now supported to load a different configuration file
with the CONFIG keyword.
* Fix API call 0x0019 (Read Disk.)
* MENU AUTOBOOT, MENU TABMSG, MENU PASSPROMPT allows
internationalization of menu messages.
* A new feature, TEXT HELP, allows the administrator to set
a multi-line help message for individual selections.
* Fix API call 0x0012 (Cleanup, shuffle and boot.)
* New API call "Cleanup, shuffle and boot to flat protected mode"
* New API call "Cleanup, shuffle and boot to real mode",
similar to API call 0x0012 but allows arbitrary register setting.
* Introduce a library interface for loading arbitrary binary
formats with relatively easily understood code. See
the elf.c32 module for an example on how to use it.
* New module "elf.c32", to load a protected-mode ELF kernel.
* MBR (old and new): Fix bug in CHS mode when LBA >
* vesamenu: fix decoding of palettized PNG images.
* Update the Linux kernel boot protocol.
* PXELINUX: Press Ctrl-N at the boot prompt to read out the
* Instead of the (non-existent) MAC, use the client identifier
for networks like Infiniband and Firewire/1394.
* Add a new INCLUDE command to the core syslinux parser.
* Allow binding help text to F11 and F12.
* F-key help now available in the simple menu system.
* Disabled the polling for ARP during idle. It is simply too
slow on some (broken!) PXE stacks.
* PXELINUX: also try to fetch the config file based on UUID.
* SYSLINUX/EXTLINUX: New RAID mode (-r) which calls the BIOS
to load the next device (typically the next drive) on boot
Changes in 3.36:
* MEMDISK: Disable EDD by default on floppy disks. EDD can be
enabled with the "edd" option and disabled with "noedd".
This (hopefully) should make Ghost work again.
* SYSLINUX: "unix" installer now uses Linux ioctls instead of
* New MBR which can boot from logical partitions.
* SYSLINUX: Fix bug in detecting special extensions which was
introduced in 3.35 :(
* PXELINUX: Unbreak chainbooting FreeBSD (and possibly others.)
Changes in 3.35:
* MEMDISK: New "safeint" mode.
* MEMDISK: Be more compliant with the PnP BIOS spec.
* MEMDISK: Turn on EDD support by default.
* MEMDISK: Try to work on some machines on which it would not
work when there was no floppy drive in the system.
* Simple menu system: fix serial console support (broken in
* SYSLINUX: Support subdirectories. Like ISOLINUX, the
"current directory" is the directory in which syslinux.cfg
is found; this is searched for in the sequence
/boot/syslinux, /syslinux, /. As a side benefit, label names
like "linux-2.6.18" and "linux-2.6.19" are now supported.
To install ldlinux.sys in a subdirectory, pass the -d
directory option to the SYSLINUX installer.
This work was sponsored by slax.org (thanks, Tomas!)
* New API call: read disk.
* Invoke ONERROR on initrd load failure.
Changes in 3.31:
* The simple menu system (menu.c32 and vesamenu.c32) now
support loading more than one configuration file at a time,
using MENU INCLUDE or by specifying multiple filenames.
* The MENU COLOR statement can now control the shadowing mode.
Changes in 3.30:
* libcom32 extended to support graphics mode and graphical console.
* vesamenu.c32, new graphical version of the Simple
Menu System, see README.menu.
* New com32 modules by Erwan Velu do selection based on CPUID
or PCI devices present.
* RPM spec: add syslinux-tftpboot module; move syslinux by
default to the /usr/share/syslinux directory.
* RPM spec: extlinux is now a separate package.
Changes in 3.20:
* EXTLINUX: New options --install (-i) and --update (-U), to
make it clear if a boot loader should be installed or
updated. For now, defaults to --install for compatibility;
a future version will require one of these options.
* New library functions to load and place files in memory.
* mboot.c32 bug fixes.
* Remove 8 MB kernel size restriction.
* Add "klibc" target for building unix/syslinux and
extlinux/extlinux with klcc (klibc-1.4.27 or later.)
* PXELINUX: Fail (and eventually reboot) if no configuration
file was found.
* COM32 module by Erwan Velu to make decisions based on DMI
* Fix issue where going back and forth between menus a lot
would cause a hang.
* ISOLINUX: Fix bug which made "cd boot sectors" not work.
Changes in 3.11:
* MEMDISK: Fix bug by which accessing the real floppy disk
as B: in MS-DOS was broken.
* Simple menu system: allow tweaking of the screen layout.
* Simple menu system: better command-line editing, correctly
handle command lines above 256 characters.
* PXELINUX: revert memory allocation change that caused
problems on some network cards.
* MEMDISK: Try work around a bug on some BIOSes when no
physical floppy disk is present in the system.
* Enable the 16550A FIFOs, if present, when doing serial
* New "totaltimeout" command establishes a timeout without
regard for any user input.
* Simple menu system: timeout behaviour now more in line with
* Simple menu system: "ontimeout" should now work correctly.
Changes in 3.10:
* gcc 4.0.1 compilation fixes.
* Add support for querying the PCI BIOS in libcom32
(used by ethersel et al.)
* Fix PCI handing (ethersel etc) on several old chipsets (and
* Try to deal with systems with broken EBIOS.
* New API call to do "localboot".
* New API call to query features.
* New API call to run kernel image, a lower-level call than
"run command". See comboot.doc.
* Fix for bug in EBIOS code discovered by Arwin Vosselman.
* NOESCAPE security fix.
* Comments are now recognized even without a space following #.
* Fix incorrect handling of mixes of entries with and without
* The idle API call now harmlessly returns failure if it is a
no-op. That way the caller can decide whether or not to
bother invoking it again.
* Temporarily disable the idle API call on PXELINUX, due to
some platforms on which the idle API call seems to hang; this
problem has not yet been debugged.
* MEMDISK: the handling of DOSEMU-headered images was broken;
* EXTLINUX: symlinks are now supported.
* Simple menu system: N and P now work correctly as hotkeys.
* MEMDISK: more BIOS bug workarounds.
Changes in 3.09:
* gcc4 compilation fix.
* <BEL> (Ctrl-G) in message files now causes a beep.
* Reduce the command line to 511 characters; 1023 caused
Changes in 3.08:
* SYSLINUX: Fix performance regression (-s mode always
* Add API function for idle loop.
* libutil: Add do_idle() function for idle loop, make
get_key() use it.
* libutil: Add SHA-1 and base64 functions.
* Simple menu system: add password support.
* EXTLINUX: Sparse files now handled correctly.
* EXTLINUX: Large directories now handled correctly.
* ALL: At the prompt, Ctrl-X now forces text mode.
* Fix configuration file parsing error, that could cause
* Rewritten advanced menuing system from Murali Ganapathy.
* MEMDISK: New "bigraw" mode to work around certain broken
BIOS flash programs.
* COM32 module to boot Multiboot systems, including Xen. See
* Max command line changed to 1023 characters. Note that the
kernel proper still can only handle 255 characters without
patching, and COM16 binaries can only handle 125 characters.
Changes in 3.07:
* Fix chainloading (chain.c32).
* Fix zlib build problem.
* Use a private copy of <linux/ext2_fs.h>.
Changes in 3.06:
* Fix typo that caused the ramdisk to load in the wrong place.
Changes in 3.05:
* New API function "shuffle and boot"; allows COM32 modules to
load or construct (almost) arbitrarily complex objects,
e.g. a kernel and its initrd/initramfs in pieces, and have
the API core reorganize memory for booting. (A library API
for this function will be introduced in a later version.)
* The initrd= option now supports multiple filenames separated
by commas. This is mostly useful for initramfs, which can
be composed of multiple separate cpio or cpio.gz archives.
(Note: all files except the last one are zero-padded to a 4K
page boundary. This should not affect initramfs.)
* EXTLINUX: Fix API function 000Ah (get derivative-specific
* libcom32/ethersel: Support PCI Config Mechanism #2 on
machines still infested with that hideous old hack.
* SYSLINUX: Fix directory-parsing bug.
Changes in 3.02:
* SYSLINUX: The "unix" installer now sets the MS-DOS
attributes (hidden, system, readonly.)
* COM32 library: build the .lnx (test modules for running
under Linux) as architecture native modules, in case
i386 devel libraries aren't installed.
* EXTLINUX: Hack for systems which don't have BLKGETSIZE64
defined in the standard header files.
* Simple menu system: minor aestetic improvements, and try to
work better over a serial console (speed, and readability on
monochrome terminal emulators.)
* New CONSOLE directive to control output on the video console
(useful for dealing with some broken serial-forwarding
* New com32 module "ethersel" for searching for an Ethernet
card and selecting the proper version of Etherboot.
* EXTLINUX: Allow the user to override the detected geometry.
Changes in 3.01:
* EXTLINUX, SYSLINUX: Fix compile errors on some systems.
* EXTLINUX: Default to zipdrive geometry (64 heads, 32
sectors) if no other geometry can be detected.
Changes in 3.00:
* SYSLINUX: Support FAT32 and EDD. As an unfortunate
consequence, LDLINUX.SYS is no longer an ordinary file; it
is block-mapped at install time, which means it can only be
written using the syslinux installers.
* SYSLINUX: Reorganize the source code for the installers;
each one of the installers (dos, win32, unix, mtools) is now
built in its own subdirectory. In particular, "mtools" is
the unprivileged installer which uses mtools; "unix" is the
privileged installer which uses system calls.
* SYSLINUX: Completely rewritten DOS installer in C.
* ALL: "label" statement information is now stored in a
compressed format, which means that a lot more labels are
permitted (500-1000 in a typical configuration, but depends
on the complexity.)
* EXTLINUX: New derivative, which boots from an ext2/ext3
* SYSLINUX: The DOS and Win32 installers can now optionally
write the boot sector to a file instead of the real boot
sector. This is not supported in the Linux installers,
* ALL: New NOESCAPE command, disables the "hold down the Shift
key to display the prompt" behaviour.
* New simple menu system, as an alternative to the advanced
menu system already present. See README.menu for details.
* PXELINUX: Filenames can now be prefixed with an IP address
or DNS name plus :: (e.g. 192.0.2.1::filename or
server.domain.com::filename), which downloads a file from an
alternate TFTP server, or just a :: (e.g. ::filename), which
suppresses the common pathname prefix. See pxelinux.doc.
* SYSLINUX: Add an -m option to the DOS and Win32 installers
to write an MBR and -a to mark the partition SYSLINUX is
being installed on active.
* MEMDISK: Give a way to query the boot loader type while
running MEMDISK; see memdisk/memdisk.doc and
* mkdiskimage: substantially improved mkdiskimage which, among
other things, can now be used to initialize USB keys as
zipdrives; see README.usbkey for more information.
Changes in 2.13:
* MEMDISK: Fix command-line parsing "brown paper bag" class
* MEMDISK: Add "raw" mode to support the DOS boot disk from
WinME/XP, which seems to deliberately crash the system
when someone uses the "INT 15h mover" highmem API.
* Make "make install" do something sane for the com32
* In the spec file, create a separate -devel RPM for the com32
Changes in 2.12:
* Simple C library, based on klibc, for writing COM32
* Fix the handling of file length in loading of COM32
* MEMDISK: Work around a linker bug by rearranging the code to
not use the linker for the 16-bit code.
* SYSLINUX: If we're building on a machine without a Win32
(mingw) compiler, just skip building syslinux.exe.
* ISOLINUX: Support non-mkisofs mastering programs, at least
as long as the image is single-session. For best results,
ISOLINUX should be the only boot loader installed.
* MEMDISK: Allow the user to specify that the simulated disk
should be write-protected.
Changes in 2.11:
* ALL: Add an API call to get the configuration file name.
* SYSLINUX: Fix bug in 2.10 that prevented it from working
correctly for a lot of people.
* SYSLINUX: In the installer, make mtools a bit less fussy.
* Make the menu system compile with newer gcc's.
Changes in 2.10:
* MEMDISK: Handle images compressed with zip as well as with
gzip. Some Windows-based image tools apparently generate
these kinds of images by default. Patch by Patrick
* Major menu improvement from Murali Ganapathy.
* ISOLINUX: Wonderfully sick and brilliant workaround for
severe bugs in certain Award BIOSes; from Knut Petersen.
* SYSLINUX: Fix for the nomtools installed, from Frederic
* PXELINUX: Fix handling of IP numbers in the ranges
100-109 and 200-209.
* ALL: New option "allowoptions" (defaults to 1), which
controls if options are allowed on the command line or not.
* SYSLINUX: Support building under klibc (see the klibc
distribution for details.)
Changes in 2.09:
* SYSLINUX: Remove residual setuid crap from
* Handle video pages correctly when using the API functions.
* Handle compiling on an x86-64 platform correctly.
* Menu system from Murali Krishnan Ganapathy; see the menu
directory for information.
* COMBOOT: Allow COMBOOT programs to change screen text mode.
* COMBOOT: Correct the documentation of how to detect
SYSLINUX from COMBOOT!!!!
* COMBOOT: Fix "get key without echo" API function.
* SYSLINUX: Fix bug that affected the API open function.
* ALL: Improve the E820 memory parser, to work around some
Changes in 2.08:
* Add new configuration command "ontimeout" to allow timeout
to have a different action than just pressing Enter.
* Add new configuration command "onerror" to allow a custom
command to be executed in case the kernel image is not found.
* Fix bugs in the COMBOOT/COM32 command-line parsing. APPEND
now works with COMBOOT/COM32 images.
* PXELINUX: Poll for ARP requests while sitting at the
prompt. This makes some boot servers a lot less unhappy.
* PXELINUX: Actually free sockets when we get a failure
(including file not found.) This bug would cause us to run
out of sockets and thus "go deaf" after a while.
* MEMDISK: Add an API to query for the existence of MEMDISK.
* SYSLINUX: Fix loading boot sectors (.bs/.bss) from floppy
* .c32 is now one of the extensions searched for
* PXELINUX: RFBG.exe seems to randomly overwrite memory
location 0x5700. Thus, don't use it!
* PXELINUX: Change pathname length max from 63 to 127; change
max vkernels from 128 to 64.
* Support Ctrl-U -> kill entire command line input.
* The "samples" directory contains a (barely at all tested)
chain loading example, chain.c32, which may be used to
chainload local floppy disks and hard disks. Use with
"chain fdN" or "chain hdN [partition]"; N = 0 for the first
drive of each type.
Changes in 2.07:
* MEMDISK: Workaround for BIOSes which go into a snit when
they get a RESET command for the floppy system when there is
no floppy in the system.
* PXELINUX: Add "ipappend 2", which passes the hardware
address of the boot interface to the kernel as a
* mkdiskimage: fix the generation of the end limit.
* PXELINUX: Fix multiple bugs in chainloading of other NBPs.
* MEMDISK: Fix bug that would occationally cause "ran out of
input data" when using compressed disk images.
* SYSLINUX: Updates for the win32 installer (from Lars Munch.)
* PXELINUX: PXELINUX-specific options are now recognized both
in a vendor-option-space (a.k.a. type 43 encapsulated) as
well as in a site-option-space (unencapsulated.)
* COM32: Don't crash when DS != 0.
* COMBOOT/COM32: Make file reading work correctly. Thanks to
Phung Chi Kien for submitting a test program.
Changes in 2.06:
* ALL: Fix problem that would occationally cause a
boot failure, depending on the length of the kernel.
* ISOLINUX: Fix problem that would occationally cause a
boot failure, depending on the length of directories.
* SYSLINUX: Win32 installer now flushes buffers.
* ppmtolss16: Be fully compliant with the PNM spec;
actually process comments in the header and odd
alignments of the various parameters, as well as
"plain" (not raw) files and PBM and PGM files.
* PXELINUX: Lower the default MTU to 1472 in order to deal
with systems with slightly nonstandard MTUs, and PXE
stacks which don't defragment correctly. Unfortunately this
is very hard to test dynamically.
Changes in 2.05:
* PXELINUX: Add a default query based on the hardware address
of the boot device. This is in lower case hexadecimal form
separated by dashes and including the hardware type, for
example, the Ethernet (type 1) address 88:99:AA:BB:CC:DD
would query the file pxelinux.cfg/01-88-99-aa-bb-cc-dd.
* PXELINUX: Fix bug involving non-IP-based config file names.
* SYSLINUX: New installer for WinNT-based systems, from Lars
* MEMDISK: Fix handling of memory region overlap when
decompressing. Thanks to Mikhail Kupchik for identifying
Changes in 2.04:
* ALL: Reclaim even more low memory by observing that
comboot_seg == real_mode_seg is perfectly fine, and by the
fact that the 1000h segment managed to get unused in all
* PXELINUX: Attempt to negotiate full Ethernet-sized blocks
(1468 bytes) using the blksize option.
* SYSLINUX: Resurrect the old no-mtools version of the
installer, although as a root-only tool. Some distributors
have indicated that they need a small standalone installer.
* MEMDISK: Fix a memory offset computation error when
installing compressed disks which generally would cause
1 MB of memory to be wasted.
* MEMDISK: Fix installing the E820 memory map. Calling
INT 15h AX=0E820h with MEMDISK 2.03 loaded would give a
completely corrupt memory map.
* SYSLINUX: Make libsyslinux a dynamic library, so that it can
be updated separately from client programs. The whole idea,
after all, is to enable alternate programs to become
* Include an rpm spec file in the distribution, so rpmbuild
Changes in 2.03:
* Actually support comment lines in the configuration file.
* PXELINUX: Try to resolve some problems with stack switches.
* PXELINUX: Handle PXE stacks with broken routing.
With these workarounds, the remote install PXE boot floppy
(rbfg.exe) from Argon Technologies should work correctly.
* Fix problems with Perl scripts in UTF-8 locales.
* You probably need NASM 0.98.34 or later to compile this
version. 0.98.36 is recommended.
* MEMDISK: Now supports gzip compressed images.
Changes in 2.02:
* SYSLINUX: Security flaws have been found in the SYSLINUX
installer when running setuid root. Rewrite the SYSLINUX
installer so it uses mtools instead. It therefore now
requires mtools (specifically mcopy and mattrib) to exist on
your system, but it will not require root privileges and
SHOULD NOT be setuid.
Changes in 2.01:
* MEMDISK: Fix memory sizing bug when the ramdisk crosses the
16 MB boundary.
* MEMDISK: Add a "pause" option to stop immediately before
booting, to read off the messages.
* MEMDISK: Support disk images with DOSEMU headers.
* Update the mkdiskimage script to handle newer mtools
versions, and be able to generate disk images with DOSEMU
headers (controlled by the -d option).
* Fix the COM32 sample program.
* PXELINUX, ISOLINUX: Fix some COMBOOT API calls.
* PXELINUX: Doc fix.
* Build SYSLINUX into a small library for encapsulation into
other programs (however, please keep in mind this is a GPL'd
* SYSLINUX: Make installer work with "owner" in /etc/fstab.
* SYSLINUX: Fix issue with working on nonpartitioned hard disk
devices. THIS CONFIGURATION IS NOT RECOMMENDED.
Changes in 2.00:
* ALL: Add support for "COM32" (32-bit COMBOOT) images.
* ALL: Add an API for COMBOOT/COM32 images. See comboot.doc
for details. There is a C development environment for
COM32 being created; it should be ready at some point in
* Fix mbr.asm so that it actually works.
* SYSLINUX: The syslinux installer *SHOULD* now be safe to
run setuid root.
* PXELINUX: Fix bug where PXELINUX would override random
chunks of the UNDI code segment! Thanks to Kevin Tran for
finding this bug.
* ISOLINUX: Fix a bug related to slashes in pathnames.
* ISOLINUX: Fix a bug in handling initrds over 128 MB.
* ALL: Make the <Ctrl-V> key print out the version; this is
to help debugging.
* Add a small script, mkdiskimage, to create a DOS-formatted
hard disk image using mtools. This may be useful in
conjunction with MEMDISK.
* ISOLINUX: Search for a /boot/isolinux directory as well as
* ALL: Fix a bug related to very long configuration files.
* PXELINUX: Work around a NASM bug which would result in no
delay before reset if an error occurs.
Changes in 1.76:
* ISOLINUX: Remove code no longer used which caused hangs on
some Toshiba laptops.
Changes in 1.75:
* ALL: NASM 0.98.32 or later is now required to build
SYSLINUX from sources.
* SYSLINUX: put back in the workaround for the BIOS floppy
table. This seems to be a requirement for "extended" floppy
formats to work correctly.
* SYSLINUX: No longer warn if one is trying to boot on a 286
or older. The above BIOS workaround no longer fits if the
requirement to use only 8086-compatible code in the early
boot is maintained. It made sense in 1994, but in 2002 a
286 or older is a museum object.
* SYSLINUX: Use a downright bizarre, stateful algorithm to try
to guess the maximum transfer size. I am *hoping* this will
cut down on the number of systems for which -s is required
to work at any acceptable speed.
* ISOLINUX: Add a few more workarounds for various broken El
* Make sure .depend files aren't accidentally packed...
* ALL: Fix bugs in the extension-detect code; this caused
files like COMBOOT images and CD boot sectors to be
mis-identified as Linux kernels and rejected.
* ALL: Fix the return from COMBOOT.
* ALL: Do some of the early groundwork for supporting DOS
system calls in COMBOOT.
* Get rid of unnecessary "near" directives, making the code
* PXELINUX: Put the PXE stack back in the init state before
invoking a chain-loaded NBP.
* PXELINUX: Actually found the combination of calls that
allows some (most?) PXE 2+ stacks to be unloaded from memory
* PXELINUX: Add "keeppxe" command-line option to disable
the standard unloading of the PXE stack.
Changes in 1.74:
* SYSLINUX: fix bug that would cause valid kernel images to be
Changes in 1.73:
* Work on removing gratuitous differences between modules.
* Break up the source in common and module-specific files.
* PXELINUX: Allow chaining of other PXE NBPs.
* ISOLINUX: Allow loading "CD-ROM boot sectors".
* ALL: generalize the definition of a boot sector/NBP.
Changes in 1.72:
* PXELINUX, ISOLINUX: Fix bugs in the new core code.
Changes in 1.71:
* Fix a "brown paper bag" class bug in the new core code.
Changes in 1.70:
* Major code restructuring.
* Relax the conventional memory limits somewhat.
* MEMDISK: Set up the "version number string" pointer in the
* SYSLINUX: Fix, again, "the bug that won't die": the use of
the offset parameter with the SYSLINUX installer.
* SYSLINUX: Fix possible superblock corruption problem in the
Changes in 1.67:
* Handle bug in the location of initrd.
Changes in 1.66:
* MEMDISK: Make compile with newer versions of gcc.
Changes in 1.65:
* ISOLINUX: Support booting disk image files (to boot DOS or
other non-Linux operating systems), *IF* the BIOS works
correctly; unfortunately many BIOSes apparently don't.
* Support Linux boot protocol version 2.03 (explicitly
specify the initrd address limit.)
* Handle small "pseudo-kernels"; images that use the Linux
kernel boot protocols but are less than 64K in size.
* MEMDISK: New subsystem; this is a driver which allows
legacy OSes to boot using an in-memory simulated disk.
See memdisk/memdisk.doc for more info.
* PXELINUX, ISOLINUX: Correctly handle files larger than 65535
blocks (32 MB for PXELINUX, 128 MB for ISOLINUX.)
* PXELINUX: Make a best-effort attempt at freeing all memory
claimed. From the looks of it, it will fail on most PXE
Changes in 1.64:
* Limited support for hardware flow control when using a
serial port console.
* Support specifying the serial port I/O address explicitly.
* Make DOS installer hopefully behave more nicely when used on
recent Windows versions.
* Fix returning to text mode when a font has been specified.
* Attempt to detect missing serial port hardware and disable
the serial port if there is nothing there.
Changes in 1.63:
* Make the ppmtolss16 program handle color conversion more
* Clean up "make install" target, honour INSTALLROOT if it
* SYSLINUX: Fix stack-smash bug identified by Steffen
* Hopefully fix return-to-text-mode on some graphics cards.
* ISOLINUX: Bug workaround for Award BIOS 4.51, and perhaps
other buggy BIOSes as well.
Changes in 1.62:
* PXELINUX: Allow the DHCP server to override the
configuration file name and pathname prefix, using
"site-specific" DHCP options.
* PXELINUX: Documentation fixes.
* PXELINUX: Fix the "ipappend" option; the last two values
were reversed vs. what the kernel expected.
* Introduce a way to return to text mode once we are already
in graphics mode. This may be useful for F-key help
* Fix several bugs in the way return to text mode was handled.
Changes in 1.61:
* ISOLINUX: Support full pathname searches. Max length for a
pathname is 255 characters. As a result, only 64 "label"
statements are supported in ISOLINUX.
* PXELINUX: Max filename length extended to 63 characters.
Changes in 1.60:
* Add support for graphical splash screens.
* Add mode control characters, which allows you to control
message display output depending on output mode (text,
graphics, or serial port.)
* ISOLINUX: New program, which boots Linux from a CD-ROM
without using floppy emulation mode. See isolinux.doc for
* PXELINUX: Don't search for boot sector file types, since
they don't work anyway.
* SYSLINUX: Document the LOCK command for Win9x, and the error
dialog box for WinNT/2K.
Changes in 1.54:
* PXELINUX: Fix code for finding !PXE from PXENV+. This was
due to a spec bug; match the most recent spec since that
seems to be what implementations actually do.
* SYSLINUX: Add some smarts to the boot sector, which
hopefully should reduce the number of systems which require
stupid mode ("syslinux -s").
* PXELINUX: Document further some of the pathologies with old
* When specifying a "default" command line, no longer
automatically appent "auto". See the "DEFAULT" command in
syslinux.doc for more information.
* PXELINUX: Clean up the allocation of local socket numbers.
Changes in 1.53:
* PXELINUX: Rename pxelinux.bin to pxelinux.0, to match what
most PXE servers seem to expect.
* PXELINUX: Update the DHCP/boot server setup documentation.
* PXELINUX: Support new "localboot" option for "label"
* PXELINUX: More robust parsing of DHCP/boot server packets.
* PXELINUX: Include a small utility program "gethostip" to
compute hexadecimal IP addresses.
Changes in 1.52:
* PXELINUX: Fix bugs introduced by new A20 code. (SYSLINUX
has also been changed for code consistency reasons, but I'm
pretty sure the changes are don't care on SYSLINUX.)
* Documentation updates.
* PXELINUX: Add "ipappend" option to generate an ip= option to
Changes in 1.51:
* PXELINUX: Not all PXE stacks fill in the IP address for a
type 3 cached info query. Use a type 2 cached info query
for this information (only.)
* Yet another attempt at A20 coding. Now support BIOS call
15:2401 as well, and handle machines which always have A20
* Support memory detection using INT 15h, AX=0E820h. BIOS
manufacturers have apparently gotten sloppy about keeping
INT 15h, AX=0E801h working properly.
* Don't issue <CR><LF> onto the serial port when we're doing
Changes in 1.50:
* Yet another A20-code update. It seems some "legacy-free"
machines and embedded gear simply don't have a KBC to talk
to, and that waiting for one will wait forever. Sigh.
Changes in 1.49:
* SYSLINUX: Implement a hack for BIOS drivers which hog significant
chunks of low memory during boot. (Note: PXELINUX already
had this modification. SYSLINUX does still require that the
low 512K is available; PXELINUX requires 384K. Machines
with a physical memory hole in the low 640K cannot boot
Linux no matter what.) Depending what the reason is for the
memory hole, a new kernel (2.4.0-test3-pre3 or later) may be
* SYSLINUX: Default installer binary now compiled against
glibc 2.1. If this is inappropriate for your system and you
still want to use the offical version of SYSLINUX, please
follow the instructions in "distrib.doc" to rebuild the
* SYSLINUX: Linux installer program now supports -o <offset>
option which does a loopback mount with the
-o loop,offset=<> option. Useful to run SYSLINUX on an
individual partition of a whole-harddisk image.
* Include the source code to a Master Boot Record (MBR)
functionally equivalent to the one installed DOS except it
includes EBIOS support, and should be resistant to geometry
changes. The MBR code is public domain.
* PXELINUX: Fix "double p" bug: if the tftp prefix was null,
all filenames would get a "p" preprended, e.g.
"ppxelinux.cfg" and "pvmlinux".
Changes in 1.48:
* PXELINUX: Workaround for PXE ROMs based on the Intel PXE PDK
3.0 build 071 and earlier: missing !PXE structure pointer.
* PXELINUX: Handle larger BOOTP/DHCP packages.
* PXELINUX: The command line passing was broken; fix.
* PXELINUX: Make COMBOOT images work.
* PXELINUX: Documentation on how to make booting work using
the PDK 3.0-derived clients, which aren't so generous as to
allow booting with only "PXEClient" specified.
Changes in 1.47:
* PXELINUX: RFC 1123 states that a TFTP implementation MUST
use adaptive timeout, "at least an exponential backoff of
retransmission timeout is necessary." Implement a very
simple exponential backoff for retransmits.
* PXELINUX: Updated documentation, including pointer to new
* PXELINUX: When sending ERROR due to bad OACK, use the proper
destination port number (why are TFTP port numbers so odd?)
* PXELINUX: If the boot dies in the middle somewhere,
eventually give up and reset the machine (unattended
Changes in 1.46:
* New program PXELINUX to do network booting using a
PXE-compliant (Pre-Execution Environment) network booting
PROM. See pxelinux.doc for details.
Changes in 1.45:
* Serial console support. See syslinux.doc for details.
Changes in 1.44:
* Change HIGHMEM_MAX to 38000000h to (hopefully) avoid the
kernel stepping on it; 3f000000h was apparently a higher
limit than the kernel used!
Changes in 1.43:
* Add sys2ansi.pl script to display the contents of a
colorized SYSLINUX file.
* Changed the io_delay once again, after a report that the
old delay port causes hangs on some systems.
Changes in 1.42:
* Frob the "fast A20 gate" port as well as the keyboard
controller; will this help systems with problems?
* Be even more paranoid about A20, unfortunately even this
seems to be not paranoid enough... what I don't understand
is that if there is hardware out there *this broken*, how
can it run Linux at all? Report an error message rather
than hang forever if A20 is stuck.
* Include some intermediate files in the distribution, plus
provide a "make installer" target for distributors to relink
the install programs only. I would prefer the syslinux boot
loader proper to be "binary clean" for debuggablity -- use
"make clean ; make installer" to rebuild the installers only.
Changes in 1.41:
* Don't get confused by directories, volume labels, or VFAT
* Use INT 15h, AX=0E801h to query memory size before trying
INT 15h, AH=88h. This not only provides more headroom
between the kernel and the initrd on large-memory machines,
but it appears some recent BIOSes actually have started
returning garbage for the AH=88h (older) call.
* Trust high memory beyond the 15 MB mark if the user has
specified it, or if obtained with INT 15h, AH=0E801h (with
no memory holes above 1 MB.)
Changes in 1.40:
* Increase A20M delay and put in a test to avoid problems on
certain IBM Thinkpads (thanks to Donnie Barnes of RedHat
for vital info on this one.)
* Support COMBOOT style boot command images.
* Support chain loading (foreign operating systems, e.g. DOS).
* Include a new "copybs" DOS utility to copy a boot sector to
a file (under Linux, use "dd".)
* Fix the DOS installer to work for disks over 32 MB.
* SYSLINUX should now handle disks with more than 65536 tracks.
Changes in 1.37:
* Fix a bug that caused "label" statements in syslinux.cfg to
not be handled properly.
* Updated the documentation. Among other things, we now allow
up to 128 "label" statements.
Changes in 1.36:
* Fix for booting old (pre-initrd) kernels.
* It seems at least some versions of OS/2 doesn't set up all
the fields in the superblock correctly. Account for that.
* Fix bug that caused boot failure when using the mem= option.
Changes in 1.35:
* Loading from partitions now should work properly. (Actually
tested, this time. You should even be able to dd a floppy
to a partition and boot from it.)
* Removed large workaround code for an alleged ancient BIOS
bug I have never actually seen. The -s option should work
on those machines, anyway.
* Support for simple keyboard remappings, same as used by
LILO (once again to support localization.) The program
keytab-lilo.pl from the LILO distribution included to
generate such maps.
* Added a "safe, slow and stupid" (-s) option to the
installers. This option will lobotomize the boot sector to
hopefully work on even very buggy BIOSes.
Changes in 1.34:
* Ability to load a VGA font on bootup (for localized Linux
Changes in 1.33:
* Bug fix in the Linux installer.
* Added a workaround for a bug in certain AMI/Intel BIOSes
when booting from CD-ROM.
* Documentation changes.
Changes in 1.32:
* FAT16 filesystems are now supported.
Changes in 1.31:
* Now compiles under Linux, using NASM, rather than using
Turbo Assembler under DOS. See http://www.cryogen.com/Nasm
for information about NASM.
* Linux-hosted SYSLINUX installer, as well as a
rewritten DOS installer (now is written in assembler, so we
don't need Turbo C.)
Changes in 1.30:
* Added support for loading bzImage and initrd loading, and made
SYSLINUX new-setup-code aware (SYSLINUX 1.30 id=0x31).
* Added LILO-style kernel labels; see the LABEL and IMPLICIT
keywords in README file.
* Added support for colorization of intro and help screens.
* The vga= option is now handled correctly.
* Massive rewrite of large chunks of the code in order to
support the first two new features.
Changes in 1.20:
* Added simple online help at the "boot:" prompt.
* Removed 2880K image as I no longer have access to such a
floppy drive. (Donations accepted!!)
* Decided to distribute the source in a subdirectory rather
than in a nested zipfile.
Changes in 1.11:
* Removed a sanity check which would cause booting to fail on
Phoenix BIOS version 4.03. Apparently this BIOS is buggy.
Changes in 1.10:
* Added configuration file SYSLINUX.CFG. This file contains all
configurable options, and can be edited from any OS which can
access an MS-DOS filesystem; there is no longer a need to run
SYSLINUX.EXE except to write the boot sector.
* Default command line now given by "default" line in config
* LINUXMSG.TXT and BOOTMSG.TXT hard-coded file names replaced by
"display" and "prompt" lines in config file.
* LILO-style option appending now supported ("append" line in
* Prompt timeout is now supported ("timeout" line in config
file). The timeout is cancelled when anything is typed on the
* Pressing <ESC> or <Ctrl-C> at the Loading... stage now aborts
the kernel loading in progress and returns the user to the
* The installer now automatically sets the READONLY flag on
* Added 2880K disk image.
Changes in 1.03:
* Fixed bug that would prevent booting from double-density
floppies and other DOS filesystems with multiple sectors per
* Added 720K disk image.
* Changed default kernel name on disk images to LINUX.
Changes in 1.02:
* Fixed bug that would garble the command line on recent kernels
with more than 4 sectors of setup code (this wasn't really a
*bug*; rather, a kernel change broke the code. Unfortunately
the Linux boot interface is still sorely undocumented).
* Added BOOTMSG.TXT file support (message file which does not
force display of the boot prompt).
Changes in 1.01:
* Fixed bug on some (most?) 386 BIOSes would require two boot