Functional Description
5.24
Intel® Quiet System Technology (Intel® QST)
The ICH10 implements three PWM and 4 TACH signals for Intel Quiet System
Technology (QST).
Note:
Intel Quiet System Technology functionality requires a correctly configured system,
including an appropriate (G)MCH with Intel ME, Intel ME Firmware, and system BIOS
support.
5.24.1
PWM Outputs
This signal is driven as open-drain. An external pull-up resistor is integrated into the
fan to provide the rising edge of the PWM output signal. The PWM output is driven low
during reset, which represents 0% duty cycle to the fans. After reset de-assertion, the
PWM output will continue to be driven low until one of the following occurs:
• The internal PWM control register is programmed to a non-zero value by the Intel
QST firmware.
• The watchdog timer expires (enabled and set at 4 seconds by default).
• The polarity of the signal is inverted by the Intel QST firmware.
Note that if a PWM output will be programmed to inverted polarity for a particular fan,
then the low voltage driven during reset represents 100% duty cycle to the fan.
5.24.2
TACH Inputs
This signal is driven as an open-collector or open-drain output from the fan. An
external pull-up is expected to be implemented on the motherboard to provide the
rising edge of the TACH input. This signal has analog hysteresis and digital filtering due
to the potentially slow rise and fall times. This signal has a weak internal pull-up
resistor to keep the input buffer from floating if the TACH input is not connected to a
fan.
5.25
Thermal Sensors
ICH10 integrates two thermal sensors that monitor the temperature within its die. The
thermal sensors are used for Intel Quiet System Technology (Intel QST). The Intel QST
firmware can internally access the temperature measured by the sensors and use the
data as a factor to determine how to control the fans.
The ICH10 thermal sensors also provide the capability to protect the ICH10 under a
catastrophic thermal situation. When the sensors are enabled and correctly
programmed by the system BIOS, the ICH10 will shut down the system when the
ICH10 thermal limit is reached. Refer to the Thermal Memory Mapped Configuration
Registers Section 23.2 for more info on the catastrophic settings.
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Datasheet
INTEL [ INTEL ]
