T440s USB power specifications

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I'm having a little bit of hard drive trouble. When I plug them into an external multi-port, the drives click and whirl, and behave erratically. This led me to think they were bad.

But then I attached them directly to the USB ports on the thinkpad, and they worked perfectly fine. This makes me think that the external USB multiport just didn't have enough power to supply the hard drives. The multiport supplies a maximum of 5V/900ma per port.

But I am wondering, how much power do the ports on my Thinkpad T440s supply per port? I am unable to find the power specs on lenovo's website.