Nvidia 400 - Manual (Page 28)

Installation
Page 3-12
CUSB3/CUSB4: USB 2.0 ports
USB2.0 allows data transfer speed up to 480Mbps.
This mainboard includes 4 additional USB2.0 ports,
identified by two 10-pin connector.
If you wish to use the additional USB ports, install
the card-edge bracket to the system chassis then
insert its cables to this 10-pin connector.
CUSB3
CAUTION !
Please make sure the USB cable has the same
pin assignment. A different pin assignment
may cause damage to the system.
If you need the USB cable, please contact our
retailer.
CUSB4