I have recently noticed that sometimes the USB Power given out by a USB Port is not sufficient to power/use a connected device. I am curious to know if the cause of this is the Motherboard or the Power Supply? I have this problem in two of the devices I interact with: A Laptop at home, and a Desktop at work. The Laptop is my own, but the Desktop belongs to the company I work for. I think both of these are about 4 years old. I have various devices like an external HDD (powered solely through the USB Port) that do not seem to work. (I can get them to work sometimes though, but if I have too many devices like a USB to DVI, mouse, keyboard etc, they either don't connect or drop off.) Do you think that the power supply on these machines is weak i.e. putting out less current e.g. on the 5 V rail, or is it a problem on the Motherboard voltage controller/regulator? I am looking at the problem hypothetically. I am looking to build a new computer and if I know the answer to this, I can focus on getting a better component be it the Motherboard or a Power Supply. I'm just curious. Thank you all O. O.