Intel 80386 initialization

From: Vivek Mohan (vivekm_at_phreaker.net)
Date: 04/18/04 

Date: 18 Apr 2004 07:27:43 -0700

Hi,
I was reading the intel 80386 system programmers manual, the section
on initialization of the system and there was this bit about the
address lines A{31-20} being asserted -

<quote>
After RESET, address lines A{31-20} are automatically asserted for
instruction fetches. This fact, together with the initial values of
CS:IP,
causes instruction execution to begin at physical address FFFFFFF0H.
Near
(intrasegment) forms of control transfer instructions may be used to
pass
control to other addresses in the upper 64K bytes of the address
space. The
first far (intersegment) JMP or CALL instruction causes A{31-20} to
drop
low, and the 80386 continues executing instructions in the lower one
megabyte of physical memory. This automatic assertion of address lines
A{31-20} allows systems designers to use a ROM at the high end of
the address space to initialize the system.
</quote>

I am bit stumped here, but doesn't physical address mean the absolute
address in the main memory ? If so, how is 0xFFFFFFF0 a valid address
for the instruction to start at ? I think I'm missing the obvious
here. Can someone please tell me what the above passage really means ?

Vivek

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