Asus PS4 - Manual (Page 59)

ASUS RS500A-E6/PS4 4-11
7. Serial General Purpose Input/Output connectors (8-1 pin SGPIO1/2)
These connectors are used for the SAS chip SGPIO interface that controls
the LED pattern generation, device information and general purpose data.
These connectors functions only when you install an ASUS PIKE SAS RAID
card.
8. Serial General Purpose Input/Output connector (8-1 pin SGPIO3)
This connector is used for the SGPIO peripherals of the PROMISE ® RAID
SATA LED.