Some 9-pin USB headers may only have one actual USB port

[japlytic]

On a Dell Studio Slim 540s, I found that one USB port each on the F_USB3 and F_USB4 headers was not functioning.
Further investigation revealed that even though the Power (1/2) and Ground (7/8) pins on these headers were correct, Pins 3/5 (USB0 bus) were tied to GND by the motherboard, even though Pins 4/6 (USB1 bus) had a functioning USB port.
My belief is that these connectors were intended for high power devices which only require one USB bus, such as card readers.

[ratdude747]

Re: Some 9-pin USB headers may only have one actual USB port

Bus powered external USB 2.0 (not 3.0) HDDs and Optical drives were like that (as were many USB hubs), using one port for power and the other for power and data. Usb 3.0 upped the 1 port max form .5A to 1A (IIRC), so (for now) I have yet to see a usb 3.0 device with such a cable.