[LinuxBIOS] Question about protect mode?

[Feng, Libo]

Thank you, Mr. Darmawan Salihun.

I will google the key words you gave.

I am still not quite clear about the second question. Before BIOS runs, the system must know where BIOS FLASH is attached, LPC, X-BUS or PCI? How?


Best Regards

??? Feng Libo @ AMD  Ext: 20906
Mobile Phone: 13683249071
Office Phone: 0086-010-62801406

-----Original Message-----
From: Darmawan Salihun [mailto:darmawan.salihun at gmail.com] 
Sent: Wednesday, May 30, 2007 7:00 PM
To: Feng, Libo
Subject: Re: [LinuxBIOS] Question about protect mode?

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