[coreboot] legacy bios support and coreboot

aaron lwe aaron.lwe at gmail.com
Thu May 8 03:54:18 CEST 2008

>  I think coreboot only runs the vga bios and only in a simulator.  I
>  think it would be difficult to run some option roms (eg, scsi) from
>  within an emulator.  That said, I think it would be great to configure
>  which roms got run, which got emulated, and which got skipped
>  entirely.

Cool. BTW, for via epia-cn, vgabios is not run by emulator, but by
switching back to real mode and call the rom code. I think this is the
same way legacybios did. Maybe we can have a config option to let
coreboot know when we are using legacybios we can omit runnning pci
roms and let legacybios takes care, but when using other payloads, the
pci rom code should still be run by emulator or vm86.

>  That's fine, but it means the launched OS will be able to overwrite
>  the 0xf0000 segment.  It would be nice to write protect it, but it is
>  not a huge issue.

yes, the problem is legacybios cannot know all the chipsets' specific
register settings for shadow ram, so it would be impossible unless we
pass some info from coreboot to legacybios.

>  Changing the legacybios code to forward debug output to a serial port
>  will definitely help here.

thanks and I've added serial code and now able to see the output. It
seems that legacybios cannot detect the ide disk... It said: ata0
master: unknown device. Maybe the ata code is ok for qemu emulated
dirves but not for real hardware. I'll take a look at it.


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