FreeBSD, 160GB HD, and a Bios limitation

Jerry McAllister jerrymc at
Tue Nov 20 08:29:04 PST 2007

On Tue, Nov 20, 2007 at 02:18:15AM -0700, Christoper Tucker wrote:

> > 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
> geomtery.""

I can't guarantee that it applies to your situation, but I always get
those messages and just ignore them.   FreeBSD deals with it correctly.

There are some FAQs and postings in the archive and a couple of online
articles that talk about it.  I don't have time to go looking now, but
you can find it as easily as I can.


> 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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