[SeaBIOS] seabios: About the reset mem address

Peter Stuge peter at stuge.se
Thu Sep 29 02:14:44 CEST 2011

Amos Kong wrote:
>  [CS base address = CS segment selector * 16]
>        F000H * 16 = F0000H
>                     ^^^^^^ (it's not 0xFFFF0000)
> ==> "CS base address" is not "base address in CS register" ?

Study real mode vs. protected mode. x86 starts in real mode. For
backwards compatibility, 386 CPUs (the first with full 32-bit
addressing) and later also start in real mode, but with CS in a
twilight state, so that the first instruction is actually fetched
from near top of 4GB, where the boot flash chip is decoded.

> 2. If I only compile seabios, and load the bios.bin to qemu,
> coreboot will not be used?

Of course not. If you compile Linux, and load bzImage from LILO, will
gPXE be used? coreboot is one project and SeaBIOS is another. They
can both be used together and separately.

> what's the relationship between coreboot and seabios ?

coreboot picks SeaBIOS as default payload, if the person building
coreboot does not explicitly provide a payload.

On qemu the initialization done by coreboot is simple, and has been
included into SeaBIOS instead, probably for convenience, I don't


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