The HUH721010ALN600 series have supported the Power Disable pin that allows power cycling / power saving to be controlled by the host via interface pin 3. The power segment, precharge pin P3 is connected to the two V33 pins P1 and P2 on the SAS 1.1/2/2.1 drive backplane receptacle connector. But on SAS 3.0, P3 is used to redefine as a Power Disable signal: Asserted voltage (power disabled) 2.1V to 3.6V. This will cause the HUH721010ALN600 on the power disable stage. P3 is not connected behind a SAS drive plug connector if the Power Disable signal is unsupported.