[OpenBIOS] sorry to ask this again

Jeff Garzik jgarzik at mandrakesoft.com
Tue Apr 4 20:03:25 CEST 2000

Can you turn on word wrap in your mailer, Matthew?

Matthew Sullivan wrote:
> Actually from my expreience with Award and AM BIOS's they test for 55AA at A000 and then C000 looking for a mono card then then a colour booting the first card found and ignoring any second card.... (ie if a mono and colour cards are both present)....

Yep, sounds like a good plan.

> The only thing I haven't worked out is if you have a card not located in the usual position most BIOS's will still boot it... but none of the BIOS's seem to want to init any second card.... (That includes the second VGA port on a couple of twin TVGA 9000 series cards I had to work on a while ago...)

By virtue of the fact that two cards cannot share a single VGA region,
you can only init a single card.  So that makes perfect sense.  The
standard BIOS reaction to multiple video cards is to -not- execute the
BIOS init sequence for secondary/tertiary cards, but to instead disable
their MMIO and PIO decoding altogether.  This is why XFree86 must map
and execute the video BIOS for a secondary card, before it can be used
as a secondary head.

> My conclusion to this is there must be a global identifier to indicate the card is a display card... and the current BIOS's look for this so that they can determine, 1/ There is a display card in the system, and 2/ where it is ... I say this because last time I put 2 PCI VGA cards in a machine (not the same type) no matter what addresses I set them to and which slot they physically located, the same card booted each time...!?! This may be worth investigating further....

Now -that- is strange.  If there is no video BIOS in the standard
location, it would seem logical to initialize the first


Jeff Garzik              | Tact is the ability to tell a man 
Building 1024            | he has an open mind when he has a
MandrakeSoft, Inc.       | hole in his head.  (-random fortune)
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