[U-Boot-Users] why eeprom vs flash

[David Hawkins <dwh@ovro.caltech.edu>]

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).

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