Hardware help with diskonchip millennium!

Devi Priya ijpriya at hotmail.com
Mon Dec 8 08:48:19 EST 2003

On Mon, 2003-12-08 at 05:15 +0000, Devi Priya wrote:
>         In the application note (AP044) from Msystems it is given as:
>"The DiskOnChip Millennium is mapped into an 8KB memory window in the host 
>memory map. This 8KB window consists of four 2KB windows." Why is this 
>mapping done?

>The Millennium only uses a handful of those registers. There's no real
>need for the 2KiB range to be repeated -- I don't really know why it's

>Is this mapping done in hardware? I use diskonchip millennium (8MByte 
>MD2800). Then shouldn't the entire 8MB shall be mapped in hardware to the 
>physical address space?

>You can't map 8MiB into 8KiB of physical space, even if it were NOR
>flash and linearly accessible, which it's not.

I cant understand this part. I have my set up as the 8MByte diskonchip is 
mapped in hardware to the physical address from 0xFFFFFFFF-0xFF800000. 
Should I not map the entire 8 MBYte? I use sc1200 (x86 compatible).

>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 
>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 
>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
>In step 4 why is this remapping done? Is this mapping done in hardware?

>I don't know why it's done. Probably to preserve software compatibility
>with their 1980s PC BIOS extension hack, so you put your own system BIOS
>into the Millennium but keep it _separate_ from their BIOS extension
>which your BIOS is supposed to load later. You'd need chipset support
>for changing the physical address at which the DiskOnChip appears.

>        In my setup, the diskonchip is mapped in hardware to the higher 
>order address
>(0xFFFFFFFF-0xFF800000). SDRAM mapped to lower address 
>(0x00000000-0x1FFFFFF). What else
>modification do i require in HARDWARE to use diskonchip millennium?

>Probably none. See LinuxBIOS.


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