Asus RS300-E8-RS4 - Manual (Page 60)

Chapter 4: Motherboard information 4-12
8. Serial General Purpose Input/Output connector (6-1 pin SGPIO1)
The SGPIO 1 connectors are used for the Intel Rapid Storage Technology
Enterprise SGPIO interface that controls the LED pattern generation, device
information, and general purpose data.
The PSGPIO 1 and PSGPIO 2 connectors only functions when you install
an ASUS PIKE RAID card.