Asus P8B-M Series User Manual page 49

5. Serial General Purpose Input/Output connector (6-1 pin SGPIO1)
This connector is used for the SGPIO peripherals for the Intel Rapid Storage
Technology RAID SATA LED.
6. Thermal sensor cable connectors (3-pin TR1)
This connector is for temperature monitoring. Connect the thermal sensor
cable to this connector and place the other end to the device, which you want
to monitor temperature.
You can connect the thermal sensor cable to either pin 1-2 or pin 2-3.
ASUS P8B-M series 2-31