Large HD, old BIOS

[bscott at ntisys.com]

On Mon, 3 May 2004, at 10:17am, colet at code-energy.com wrote:
> That's what I was wondering.  Not knowing much of anything about hardware,
> I didn't know if the linux distro's ability to see the whole drive would
> bypass the problem of the BIOS being able to see it.

  Well, remember, "Linux distro" means a whole lot of smaller parts.  The
Linux kernel might see the whole drive, but the boot loader might not.

  When the PC is first turned on, there is no OS IDE driver available.  The
only way to read the disk is by using INT13 (software interrupt 13 hex).  
The disk controller's BIOS has to provide an INT13 interface for the disks
it controls.  If you have an onboard disk controller, that BIOS is part of
the motherboard firmware.  If you have an add-in card, it has to provide a
BIOS for that card, or you cannot boot from it (i.e., you need to boot from
another device, and then load an OS driver -- this is common with cheaper
add-in SCSI cards).

  The system BIOS (also part of the motherboard firmware), after it has
finished all the other power-on tasks it is responsible for, will look for a
bootable device.  When it finds a hard disk with the right boot signature,
it loads the first block (the master boot record) and jumps into it.  The
MBR code now has control.

  With LILO, the MBR is the first-stage boot loader.  It is responsible for
finding the second-stage boot loader (/boot/boot.b by default) and loading
that.  It has to use INT13 to do so.  The second-stage loader is responsible
for presenting the boot menu (if any), and then loading the kernel and
initrd (if any).  All of these components use INT13 (with or without LBA
extensions).  Not until the kernel is booted does the BIOS leave the
picture.

> Hmmm, that's a thought.  Anybody know of a brand/model that plays well
> with linux?

  The $50 Belkin card I bought from CompUSA works with the kernel that comes
with Red Hat Linux 9.  I'd give you a model number, but I can't find the
card right now.

-- 
Ben Scott <bscott at ntisys.com>
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