Doubt with Diskonchip millennium?

[Devi Priya]

Hi,
        In the application note (AP044) from Msystems diskonchip it is given 
as:
"The DiskOnChip Millennium is mapped into an 8KB memory window in the host 
platform’s
memory map. This 8KB window consists of four 2KB windows." Why is this 
mapping done?
Is this done for all the DiskOnChip Millennium?

The steps for BIOS is summarised as
1. After DiskOnChip Millennium BUSY# signal is negated, the CPU fetches the 
Reset Vector from
the Boot-Block area, fetches the Boot Code stored there, and starts to 
execute the code.
2. Boot Code runs the first part of BIOS, initializing the basic hardware 
functionality.
3. Boot Codes loads the rest of the BIOS from the flash memory to the DRAM, 
and transfer control
(jumps) there.
4. Chip Select of DiskOnChip Millennium is remapped from Reset Vector to 
BIOS expansion area.
5. CPU executes the rest of the BIOS code, including ROM expansion devices 
(among them, the
DiskOnChip Millennium itself).
6. CPU calls OS bootstrap loader (INT19).
7. OS is loaded, and recognizes the DiskOnChip Millennium as the boot 
device.
8. OS loads the application code from the DiskOnChip Millennium and executes 
it.
9. Application software uses DiskOnChip Millennium exactly as if it were 
using a regular hard disk.
In step 4 why is this remapping done

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