[Xorg] The big multiconsole nasty

Jon Smirl jonsmirl at yahoo.com
Mon Jul 12 09:35:07 PDT 2004

--- Egbert Eich <eich at pdx.freedesktop.org> wrote:
> Jon Smirl writes:
>  > 
>  > While trying to fix the radeonfb driver, BenH has run into some
> laptops
>  > that take the system BIOS and VBIOS, put them into a single image,
>  > compress it, and put it into a ROM. They can do this because the
> video
>  > is build into the motherboard. I don't know how you are going to
> find
>  > this without help from the system or using the C000:0 copy.
>  > 
> With some tricks (possibly by using the BIOS system vectors) you can
> often locate pages where the BIOS lives. Of course you can only use
> the pre-POSTED copy which lives somehwere beween 0xc0000 and 0xfffff.
> On these systems I have found that it is unwise to re-POST anyway
> as this may lead to undesireable results. In the best case the video
> BIOS tries to call into some vendor specific call in the system BIOS.

We know how to find the BIOS copy in low RAM. What you don't know is
which card it is associated with in a multiple graphics card system. To
track this a quirk needs to be added to the kernel which records which
device is the boot video device. The kernel need to track this since
device drivers can change the active VGA device and make another device
look like it was the boot device.

Jon Smirl
jonsmirl at yahoo.com

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