[SeaBIOS] [PATCH] Support more than one vga card

Kevin O'Connor kevin at koconnor.net
Thu May 5 02:29:37 CEST 2011

On Wed, May 04, 2011 at 11:51:02AM -0500, Anthony Liguori wrote:
> I'm a bit confused.  With sgabios, how is it normally loaded on bare
> metal?  I thought it's often just flashed in a dummy PCI device,
> make part of the BIOS image with a bios editor, or even loaded as
> part of a NICs firmware.


> Is it critical that this is loaded as a VGA rom verses a normal option ROM?

It runs as a regular option rom, but runs later in the boot.

> The only difference with VGA roms are that they are loaded slightly
> earlier in the process.

In regard to sgabios - yes.  (In general, vga roms are special in a
few different ways.)

>You shouldn't lose a lot loading them with
> normal PCI option roms.

You lose the boot menu.  If sgabios runs after other roms, then you
lose those rom's boot menus.

Not having access to the very beginning of the boot really limited
sgabios' capabilities, so the "vgaroms/" trick was added to SeaBIOS.
(In particular, one couldn't change the boot order on a real machine.)
It's ~3 lines of code though.


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