Sun Microsystems GigaSwift Ethernet Adapter Installation And User Manual page 57

Note – The link partner must be configured as link-clock slave.
To attempt to autonegotiate the link while advertising 1000 Mbps full- and half-
duplex, and link-clock auto capability to the link partner:
# boot net:speed=1000,duplex=auto,link-clock=auto,
Note – Link partner must autonegotiate in order to link-up at 1000 Mbps.
Chapter 3 Network Configuration 35