Asus RS520-E6/RS8 - Manual (Page 55)

ASUS RS520-E6/RS8 4-11
5. Serial General Purpose Input/Output connectors (6-1 pin SGPIO2/3)
These connector is used for the SAS chip SIO interface that controls the LED
pattern generation, device information and general purpose data.
These connectors functions only when you install a PIKE SAS RAID card.
6. USB connectors (10-1 pin USB34, USB56; 4-pin USB7)
The USB34 and USB56 connectors are for USB 2.0 ports. Connect the USB
module cable to the connectors, and then install the module to a slot opening
at the back of the system chassis. The USB7 connector is for a A-type internal
USB 2.0 device. The USB connectors comply with USB 2.0 specification that
supports up to 480 Mbps connection speed.
The USB port module is purchased separately.