problem with 1024 cylinders

Dan Strick strick at
Wed Sep 15 23:53:40 PDT 2004

On Wed, 15 Sep 2004 21:48:01 +0800, fancalenno at wrote:
> I have one IDE disk drive with 40GB
> ...
> my question is ... does the FreeBSD still have the restriction that its =
> root file system must be installed in the first 1024 cylinders???
> ...

On Wed, 15 Sep 2004 22:23:12 -0700, henrik.w.lund at responded:
> I think this is a rather nifty feature of the FreeBSD bootloader (the
> infamous boot0). It can boot anything from anywhere on any disk (someone
> correct me if I'm wrong here, please), provided that what it boots wants
> to boot from where it's situated. I know WinXP expects to have its
> startup files on the first partition on the first physical disk and
> refuses to start up otherwise, other OSes may have similar quirks. But
> from what I gather, FreeBSD is quite forgiving in this regard.

FreeBSD can access the entire disk once it is up an running, but the
bootstrap program used to load the FreeBSD kernel may be limited.
The FreeBSD "boot0" bootstrap program, which is sometimes confused with
the older "booteasy" program, may be configured to use either the old
or new BIOS disk functions to load the kernel.  The boot0 program is
not smart enough to determine automatically which flavor of BIOS disk
functions it should use.  It is configured by the "boot0cfg" program to
always use one or the other.  See the "packet" option on the FreeBSD
man page for the boot0cfg program.  If the boot0 program is configured
to use the old BIOS disk functions, it cannot read past the first 1024
cylinders.  If boot0 is using the new BIOS disk functions, your bootable
disk partitions can be anywhere on the drive.  This applies to any OS
you might try to boot using boot0.

To verify that you are using boot0 and to determine how it is configured,
issue a command like:

	boot0cfg -v ad0

Dan Strick

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