[U-Boot-Users] why eeprom vs flash

[Jon Smirl]

On 2/14/08, David Hawkins <dwh at ovro.caltech.edu> wrote:
> Jon Smirl wrote:
>  > I'm new to working on low level code like u-boot. Something I don't
>  > understand is why things like the Ethernet address are stored in
>  > eeprom instead of flash. Is this something to do with how boards are
>  > manufactured? From a high level perspective it doesn't seem to matter
>  > if eeprom or flash is used.
>
>
> I think you'll find varied implementations.
>
>  For example, on the MPC8349EA-MDS-PB boards, the
>  MAC addresses are stored in U-Boot environment variables
>  and they're written on the CPU heatsink base.
>
>  If you erase the Flash, then poof, gone are your MAC
>  addresses. When you Flash a new version of U-Boot you
>  need to set the IP addresses and save the environment
>  to the Flash.
>
>  I would imagine some designers prefer saving these type
>  of parameters to an EEPROM, independent of the application
>  (bootloader, kernel, filesystem, etc) flash. This would
>  cut down on the support calls from customers who erase
>  their flash and forget their MAC addresses (or can't
>  see the MAC labels if the units are installed).

How are the MAC addresses assigned? So if I order ten Ethernet chips
from Digikey will they come with something from the manufacturer
indicating which MAC addresses to use?
Or do I need to register as a vendor and get my own block of addresses?

>  So, as the designer, its up to you. But keep in mind that
>  you want to make it hard for a customer to screw up, so
>  a separate EEPROM could be a good choice.
>
>  Cheers,
>  Dave
>
>


-- 
Jon Smirl
jonsmirl at gmail.com