6Platform Notes: The Sun GigabitEthernet Device Driver • March 1999
Defining the Current Status
The read-only parameters described in TABLE2 explain the operational mode of the
interface. Based on the value of these parameters, you can determine the current
status of a link.
Flow Control Parameters
The GEM ASIC is capable of sourcing (transmitting) and terminating (receiving)
pause frames conforming to IEEE 802.3x Frame Based Link Level Flow Control
Protocol. In response to received flowcontrol frames, the GEM can slow down its
transmit rate. On the other hand, GEM is capable of sourcing flow control frames,
requesting the link partner to slow down, provided that the link partner supports
this feature. By default, GEM advertises Receive PAUSEcapability during
autonegotiation.
For normal operations, GEM doesn’t need to sourceflow control frames. However, if
GEM is operating on a slow bus (for instance, a 33-MHz PCI bus slot), and there is a
lot of frame reception activity,there could be a performance degradation due to
Receive FIFO overflow.If the link partner is capable of terminating PAUSE flow
control frames, the performance of GEM could be improved by enabling
adv_pauseTX and restarting autonegotiation.
TABLE2 Read-Only Parameters Defining the CurrentStatus
Parameter Valuesand Description
link_status Currentlink status
0 = Link down
1 = Link up
link_speed Validonly if the link is up
0 = Link is not up
1000 = 1000 Mbps
link_mode Validonly if the link is up
0 = Half duplex
1 = Full duplex
TABLE3 Read-WriteFlow Control Parameters Values and Descriptions
Parameter Values
(on/off) Description
adv_pauseTX 0, 1 TransmitPAUSE Capable (default: not capable)
adv_pauseRX 0, 1 Receive PAUSECapable (default: capable)