MSI ATX BX1 User Manual page 23

2.1-4 Fan Power Connectors: CPUFAN1/PSFAN1/SYSFAN1
These connectors support system cooling fan with +12V. It supports three
pin head connector. When connecting the wire to the connector, always
take note that the red wire is the positive and should be connected to the
+12V, the black wire is Ground and should be connected to GND. If your
mainboard got Hardware Monitor chipset on-board, you must use a
specially designed fan with speed sensor to take advantage of that.
GND
+12V
SENSOR
PSFA1
PSFA1 : Power Supply Fan
CPUFA1 : CPU Fan
SYSFA1 : System(Chassis) Fan
For fans with fan speed sensor, every rotation of the fan will send out 2
pulses. System Hardware Monitor will count and report the fan rotation
speed.
Note: 1. CPUFA1/SYSFA1/PSFA1 are the CPU, Power and Chassis
Cooling Fan Speed Connector (reserved for System Hardware
Monitor Option.)
2. Always consult vendor for proper CPU cooling fan.
2-18
GND
+12V
SENSOR
CPUFA1
GND
+12V
SENSOR
SYSFA1