FreeBSD, 160GB HD, and a Bios limitation

Christoper Tucker tucker at
Tue Nov 20 01:19:51 PST 2007

> Hi there
> I have a 600mhz PIII computer with an older BIOS that will not
> recognize my 160GB new HD that I installed for use with FreeBSD.
> I can install FBSD if I limit the drive to 32GB, but before I settle
> with that, is there a way I can access the entire drive

|Have you tried and failed to install FreeBSD?

I have successfully installed FreeBSD with the drive limited to 32GB.

I have also successfully installed FreeBSD withthe drive set to 160GB,
although FBSD seems to see only 120GB of that, and also displays the
following warning during install:

"WARNING: A gemoetry of 248015/16/63 for ad0 is incorrect. Using a more
likely geometry. If this geometry is incorrect or you are unsure as to
whether or not it's correct, please consult the Hardware Guide int he
Documentation submenu or use the (G)eometry command to change it now.
Remember: you need to enter whatever your BIOS thinks the geometry is! For
IDE, it's what you were told in the BIOS setups. For SCSI, it's the
translation mode your controller is using. Do NOT use a "physical

I did not find a solution in the documentation. Using the (G)eometry
command is something I don't understand. :) My BIOS reads the drive fine
when it is limited to 32GB, or when the drive is limited to less than 66GB
(The drive size can by limited via a utility from Seagate ... i determined
that using a size of 61GB works fine in the BIOS, but using 66BG does not
work in the BIOS. There's probably an exact figure between 61 and 66GB
where the maximum is, but I decided not to do further tests)

Here's what FDISK reports during the FBSD install:
I used the "all" command here. Using the Seagate utility, the drive had
earlier been set to 160GB, yet the installer sees 120GB here, it seems.

DMESG report here:

df -h command result here:

If FreeBSD can use 120GB of the 160GB available, that's GREAT! I'd be
happy with that. But will there be any problems since the bios reports
only that a maximum drive size of 61-66GB is OK? If I select a disk size
larger than the 61GB figure (roughly) BIOS locks up on the hard drive
menu (the computer will boot, but if i try and view the HD section of the
BIOS menu, bios locks up and i have to ctrl-alt-del).

If FReeBSD can see 120GB, what happened to the other 40GB? Is there a
danger that I could wind up writing data to nowhere or having some other
disk problem if I install FBSD this way?

|Normally the limititation is just that the root partition must be within
|the area that the bios can see.

Thanks! Chris

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