[LinuxBIOS] epia

[Stefan Reinauer]

* Tyler Pohl <tylerapohl at gmail.com> [060925 00:19]:
> I have a epia board with a VT8231 and the via C3 processor. 

What type of epia is this? There are about a dozen different epias by
now.

> I can install
> linuxbios and get it to boot with serial port output using filo.  The vga bios
> is 49kb.  Where do i insert the VGA bios is it at the begining of the flash
> chip starting at address c0000 ? 

Read the following article:

http://www.linuxbios.org/index.php/VGA_support

The BIOS is stored at the given address in flash (usually the beginning)
and copied to the ram at C000 prior to execution.

> Can I boot linux bios without fallback and
> just the normal and vga? 

There is no "normal only" but there is "fallback only". Fallback is what
you always need. 

> Is it even possible to get this vga working in
> linuxbios? 

Yes. Check http://www.linuxbios.org/index.php/FAQ and
http://www.linuxbios.org/index.php/The_EPIA-M/MII as well.

> How does the vga boot process work, I don't understand why one
> would need to insert the vga bios into the flash chip. 

Because you have no physical graphics card in the system. If you have a
PCI/AGP graphics card, this card has a small flash chip on its own,
containing the VGA bios. This VGA bios enables the graphics hardware
(enabling the RAM on the card, generating a picture, initializing
variables etc) 

Since the Epia has no graphics card but onboard graphics, you need to
pack the VGA BIOS into the system bios, thus prepend it to the system
bios.

> Couldn't one just jump
> to the vga bios instead?
 
In theory, yes. 

But VGA Bios is 16bit code, which is why we run it in an encapsulated
environment in LinuxBIOS to prevent it from messing with our clean 32bit
environment.

But of course, if you switch to 16bit and "jump to the vga bios" this
vga bios has to reside physically at some place, which for the epia
needs to be the system bios (the only flash device in the system)


-- 
coresystems GmbH • Brahmsstr. 16 • D-79104 Freiburg i. Br.
      Tel.: +49 761 7668825 • Fax: +49 761 7664613
Email: info at coresystems.de  • http://www.coresystems.de/