The KSZ8873 offers power savings at various levels. In the table on this slide, three typical power management schemes are listed. For a full description of the power management schemes supported by the KSZ8873, please refer to the data sheet. In this table, the power savings are compared to 100%, 100BASE-T traffic. The higher power down mode basically shuts down all of the circuits in the chip, but there is still a leakage of current which is why the power savings are not at 100%. The soft power down mode basically leaves the LDO circuitry on. Additionally, Microchip does offer an energy detect mode in which the circuits of an Ethernet port will be shut down if no energy is detected on that port for more than a pre-configured time duration which can range from 20ms to 5.1sec. For example, with port 1 unplugged, the transceiver circuitry is shut down while the bypass circuits are kept intact, basically sending out a pulse every second.  If a cable is then reconnected to port 1, the port will wake up. In this case, when one port is in the energy detect mode, it is estimated that a power savings of about 10% of the overall chip power consumption is achieved.