The cable allows you to connect a 2.5 " or 3.5 " SATA HDD externally to any free Power eSATA (eSATAp) port.
The Power eSATA port combines eSATA and USB and enables 5V power through the integrated USB interface.
Therefore, you do not need to provide any additional power for a 2.5 " HDD.
If you connect a 3.5 " HDD, you need to connect the IDE 4Pin connector to the motherboard power supply.
Note: For 2.5 " HDD, please do not connect the power supply! For 3.5 " HDD, please connect the power supply!