Bug 140268

Installation of FreeBSD 8.0-RC1 and 8.0-RC2 fails after the "last
chance" question with the following error:


Unable to find device node for /dev/ad0s1b in /dev!
The creation of filesystems will be aborted.

I also tried to install 7.2 and upgrade it to 8.0-RC2 (I have never
done this before and thus there is a possibility i do things the wrong
way):

freebsd-update -r 8.0-RC2 upgrade
freebsd-update install

Then I was asked to restart the system and continue the upgrade process.
After the restart, things went wrong again:

..
Trying to mount root from ufs:/dev/ad0s1a
ROOT MOUNT ERROR:

If you have invalid mount options, reboot, and first try the following from the loader prompt:
  set vfs.root.mountfrom.options=rw
and then remove invalid options from /etc/fstab
..


Motherboard used is MSI MS-7255 Ver. 1.2; HDD 80GB Maxtor PATA;
In all cases I partitioned the disk like this:
ad0s1a - 76111MB  /
ad0s1b - 2048MB swap

It makes no difference whether I use standard MBR or boot loader.
Having in mind that FreeBSD 7.2 installs (and works) flawlessly on
this hardware, I assume problem is related to broken support for any
device present in this motherboard (maybe disk controller?) rather
than hardware malfunction.

I also tried to change settings in motherboard's BIOS to different
values with no luck.  I am out of ideas what further tests I may
conduct in order to attempt to resolve this problem.

Fix: 

not known so far
How-To-Repeat: Maybe attempt to install FreeBSD 8.0-* on MSI MS-7255 motherboard?