ASROCK Rack E3C246D4M-4L User Manual page 64

REAR_FAN1
This allows you to set the rear fan 1's speed. The default value is [Smart Fan].
Smart Fan Control
This allows you to set the Smart fan's level speed.
Smart Fan Duty Control
Smart Fan Duty x (x means 1 to 11 stage)
This allows you to set duty cycle for each stage.
Smart Fan Temp Control
Smart Fan Temp x (x means 1 to 11 stage)
This allows you to set temperature for each stage.
58