On Mon, 9 Jul 2001, brianjd wrote:
> I am trying to grasp a low-level understanding of the hardware
> initialization in the boot process. When the PC first powers up, the
> processor is able to access CMOS. On some typical PC
> architecture diagrams I have seen, the processor has to traverse the
> North and South Bridge to access CMOS and the Flash BIOS. How can it
> do this without initializing these bridges? What keeps me from
> communicating directly with a USB port without bridge initialization?
There are several known-good addresses in PC bridges when they power up.
One is the POST port (0x80). Another is the FLASH boot range
0xf0000-0xfffff, and of course the PCI IO config ports, 0xcf8 and 0xcfc.
Not much else will work.
I'm not sure but are you confusing CMOS and FLASH? I'm not sure I get your
CMOS reference.
ron
