Re: grub stopped working after motherboard swap

[Jeff Sheinberg]

Ken Huisman writes:
 > Hi,
 > 
 > I was using grub on my pc to dual boot windows and linux and
 > I recently swapped out my motherboard and on the new one it
 > gives me an error.  Here are the details:
 > 
 > Old motherboard was an abit BH6, /dev/hda and /dev/hdb were
 > windows disks, /dev/hdc linux and /dev/hdd cdrom.
 > 
 > Grub booted linux and windows fine off this configuration
 > 
 > I swapped out my motherboard for an Asus A7V133
 > and now when I boot up I get the following:
 > 
 > GRUB loading stage 1.5
 > GRUB loading, please wait...
 > Error 18
 > 
 > 
 > Anybody know what this means?  I thought this error had something
 > to do with grub not being able to access the disk, but I am not sure.
 > 
 > Other info: If I boot linux off a floppy it works fine, however
 > windows ME seems to have trouble seeing the secondary IDE
 > channel (I am almost to the point of taking the whole thing back).
 > 
 > 
 > I understand there is some restriction in some cases about booting
 > off the secondary ide channel (lilo for example wouldnt boot on my old
 > m/b in this config), but given that this worked with my
 > old motherboard, I don't understand why it doesn't now.  Is there
 > something in my bios I have to tweak for grub to boot like this?
 > 

When you switch system boards, you are also changing the IDE
controllers for hd[abcd].

In order to access the correct sectors on these HDs using only the
BIOS (which is what GRUB does), then the sector mapping must be
the same (or congruent, ie, give identical results) between the
old and new controllers.

So, the BIOS has settings for LBA, NORMAL, and LARGE, which
determine the sector mappings.  On the BIOS page that allows you
to set the sector mapping will be displayed the type (LBA, NORMAL,
and LARGE), and the geometry (Cylinders, Heads, Sectors).

Now you just need to insure that the sectors mappings are
congruent between the old and new boards.

-- 
Jeff Sheinberg  <address@hidden>