[LinuxBIOS] Question about protect mode?

[Darmawan Salihun]

Feng, Libo wrote:

> > I am also confused a little. The propriety BIOS runs in the real mode, how does it test the memory beyond 1MB?
> >   
>   
The propietary BIOS such as Award-Phoenix, AMI, Insyde, etc. switches
the machine to "Voodoo Mode/Flat real mode" or
"Flat Protected Mode with no memory management scheme (as written by
Juergen)". Use google with these keywords and you will find a
lot of info in the web. LinuxBIOS is much more clean because the 32-bit
mode it uses is thoroughly defined in Intel's Manual, no confusion about
how to enter the processor operating mode. The propietary BIOSes use the
"kludge" known as "Voodoo Mode". I'm not sure whether processor
from different manufacturer will comply to it or not, because IIRC it's
quite an undocumented feature.


> > Another question is BIOS ROM can attach to XBUS, LPC, someone told me, even PCI, how dose the address forward to the location?
> >
> >   
>   
Through the chipset decoding logic. BIOS chips is partially mapped in
the "legacy part" of x86 physical address space. The chipset carry out
the tasks. Pay attention to the
chipset datasheet as you read through (and/or disassembly) the BIOS code.


--Darmawan