Hmmm, maybe I should subscribe to port-sparc, oneday, but till then...

to get the MAC address for cards used in the Ultra5, rather than the
box's own one, there is an EEPROM setting called "local-mac-address?".
Default is set to false, setting it to true causes each card to have its
own MAC address used, but this does require support in the hme driver.
I don't know how far back that particular feature is or how widespread
it is either...to quote some comments:
/*
 * To set up the mac address for the network interface:
 * The adapter card may support a local mac address which is published
 * in a device node property "local-mac-address". This mac address is
 * treated as the factory-installed mac address for DLPI interface.
 * If the adapter firmware has used the device for diskless boot
 * operation it publishes a property called "mac-address" for use by
 * inetboot and the device driver.
 * If "mac-address" is not found, the system options property
 * "local-mac-address" is used to select the mac-address. If this option
 * is set to "true", and "local-mac-address" has been found, then
 * local-mac-address is used; otherwise the system mac address is used
 * by calling the "localetheraddr()" function.
 */

For tadpole owners, another useful web page:

http://home.kabelfoon.nl/~hvdkooij/SparcBook-FAQ/sparcbook-faq.html

Darren