The 1U Passive / 2U+ Active combination solution utilizes a removable fan with 4-wire pulse width modulation (PWM) T-diode control. Use of the 4-pin PWM T-diode controlled active thermal solution helps customer meet acoustic targets in pedestal platforms through the baseboards ability to directly control the RPM of the fan
This is achieved through more accurate measurement of the processor die temperature through the processors temperature diode (T-diode). Fan RPM is modulated through the use of an ASIC located on the baseboard that send out a PWM control signal to the 4th pin of the connector, labeled Control. This thermal solution requires a constant +12V supplied to the 2nd pin of the active thermal solution.
This active thermal solution does not support variable voltage control or 3-pin PWM control. If this fan is plugged into an older 3-pin connector the fan RPM will default back and then be controlled by the thermistor located on the fan. When operating in thermistor mode, the fan speed will vary based on the inlet (T-inlet) temperature located at the fan.
This applies to: