Eeprom password is only used to control access at a PROM bootpromt level. Reboots are recorded by the OS as are failed logins - touch /var/adm/loginlog; chmod 600 /var/adm/loginlog. There is an issue in that if you enable the eeprom password and the system fails to boot automatically, it is required in order to perform a manula boot. Generally this causes problems particularly for engineers, and it is preferable to control physical access to the server (locked cabinets, passwords on console access terminal servers and keycards on machine rooms).