SGMIIって

Serial Gigabit Media Independent Interface

The Serial Gigabit Media Independent Interface (SGMII) is a sequel of MII,
a standard interface used to connect an Ethernet MAC-block to a PHY.
It is used for Gigabit Ethernet (contrary to Ethernet 10/100 for MII).
It differs from GMII by its low-power and low pin count serial interface
(commonly referred to as a SerDes).
To carry frame data and link rate information between a 10/100/1000 PHY and an Ethernet MAC,
SGMII uses a differential pair for data signals and for clocking signals,
with both being present in each direction (i.e., transmit and receive),
giving 8 signal lines in total.