Information about BIOS and the boot process
Eric W. Biederman
ebiederman at lnxi.com
Mon Mar 31 15:11:00 CEST 2003
Ivan Gustavo <ivan at munix.com.br> writes:
> I am writing some code to fixup the video chipset trident cyberblade and
> V1621 RGB->CS encoder ,
> and also trying to fix the IDE_BOOT for my mainboard (B860T or EPIA), so I am
> looking for information
> about the real bios process, and about the layout of the common bios files, and
> of course, any information
> about bios as possible.
You might try the IDE_BOOT option of etherboot...
> My main problem is to find good documentation about the post, the boot process.
> I read on some places which the CS is set F000 and EIP FFF0, so in other
> websites I had seen CS is FFF0,
> in other 000F , causing some confusion with me.
So far I have not seen a good reply so:
Since there continues to be confusion. The cpu starts running at:
0xffff0000:0xfff0 An impossible to load CS selector but the cpu manages it.
Many times there is a far jmp to 0xf000:???? so there is a rom alias there.
While not universally used in LinuxBIOS there is code present to do a short
backwards jump. And at the location of that jump transition into
32bit protected mode.
> I need some documentation about 20bits addressing lines, and the GATE A20
> function also.
As far as gateA20. It is for legacy compatibility and it has been
since the introduction of the 286. When a machine boots up all
address lines are enabled and active. When going into dos
compatibility mode gate a20 is disabled.
Under LinuxBIOS gateA20 is always left enabled.
More information about the coreboot