I have found that the respawning of consoles issue that some (including myself) experience when they run a Linux Sparc system headless, seem to have influence on the Ultra 1 ethernet lockup problem.
I have not seen any reports from users making this connection before, and therefore I think this may be of interest to some. See my description of my findings: http://www.initio.dk/linux_on_ultra1.html near the bottom of the page. There may be small disturbances in access to my webserver, since I'm about to move the system, but it should be a matter of minutes before you can connect again, if you are unable to, at first. Best regards, David List