Can FreeBSD safely use a (un-booted from) drive that is invisible to the BIOS?

[boink]

Danny,

FWIW, my FBSD 6 is running on a new "80GB" IDE disk my Asus A7V266
(Athlon mobo from end-2001) thought was 8GB in size.  I set the disk
type to manual in the (latest) BIOS, and defined the geometry as seen
by sysinstall.

It's the only device on the primary channel, running as master, CD-ROM
is on the secondary.  The system boots (no dual boot) and runs fine,
although the drive isn't listed by the BIOS at POST (the CD-ROM is)
and all disk is visible to FBSD:

# df -h
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1a    496M    126M    330M    28%    /
/dev/ad0s1d    496M    974K    455M     0%    /tmp
/dev/ad0s1e     34G    7.0G     24G    22%    /usr
/dev/ad0s1f     34G    4.5G     27G    14%    /var

However...
# cat /var/log/dmesg.yesterday  | grep ad0
ad0: setting PIO4 on VIA 8233 chip
ad0: setting UDMA100 on VIA 8233 chip
ad0: 76319MB <WDC WD800JB-00JJC0 05.01C05> at ata0-master UDMA100
ad0: 156301488 sectors [155061C/16H/63S] 16 sectors/interrupt 1 depth queue
GEOM: new disk ad0
ad0: VIA check1 failed
ad0: Adaptec check1 failed
ad0: LSI (v3) check1 failed
ad0: LSI (v2) check1 failed
ad0: FreeBSD check1 failed
Trying to mount root from ufs:/dev/ad0s1a

... which it then succeeds to do.  I'm not sure how to interpret the
'check1 failed' notices, or what GEOM means by 'new disk' at every
boot; but as it works, I'm leaving it alone.

I'm not sure if this helps.  Why don't you partition the drive, copy
whatever data you have on ad0 to it, move it to another machine, and
see what happens? At least at this point you have nothing to lose.

Best wishes,
boink