Functional Description
228 Datasheet
5.21 Thermal Management
5.21.1 Thermal Sensor
The PCH incorporates one on-die Digital thermal sensor (DTS) for thermal
management. The thermal sensor can provide PCH temperature information to an EC
or SIO device that can be used to determine how to control the fans.
This thermal sensor is located near the DMI interface. The on-die thermal sensor is
placed as close as possible to the hottest on-die location to reduce thermal gradients
and to reduce the error on the sensor trip thresholds. The thermal Sensor trip points
may be programmed to generate various interrupts including SCI, SMI, PCI and other
General Purpose events.
5.21.1.1 Internal Thermal Sensor Operation
The internal thermal sensor reports four trip points: Aux2, Aux, Hot and Catastrophic
trip points in the order of increasing temperature.
Aux, Aux2 Temperature Trip Points
These trip points may be set dynamically if desired and provides an interrupt to ACPI
(or other software) when it is crossed in either direction. These auxiliary temperature
trip points do not automatically cause any hardware throttling but may be used by
software to trigger interrupts. This trip point is set below the Hot temperature trip point
and responses are separately programmable from the hot temperature settings, in
order to provide incrementally more aggressive actions. Aux and Aux2 trip points are
fully Software programmable during system run-time. Aux2 trip point is set below the
Aux temperature trip point.
Hot Temperature Trip Point
This trip point may be set dynamically if desired and provides an interrupt to ACPI (or
other software) when it is crossed in either direction. Software could optionally set this
as an Interrupt when the temperature exceeds this level setting. Hot trip does not
provide any default hardware based thermal throttling, and is available only as a
customer configurable interrupt when T
j,max
has been reached.
Catastrophic Trip Point
This trip point is set at the temperature at which the PCH must be shut down
immediately without any software support. The catastrophic trip point must correspond
to a temperature ensured to be functional in order for the interrupt generation and
Hardware response. Hardware response using THERMTRIP# would be an unconditional
transition to S5. The catastrophic transition to the S5 state does not enforce a
minimum time in the S5 state. It is assumed that the S5 residence and the reboot
sequence cools down the system. If the catastrophic condition remains when the
catastrophic power down enable bit is set by BIOS, then the system will re-enter S5.
Thermometer Mode
The thermometer is implemented using a counter that starts at 0 and increments
during each sample point until the comparator indicates the temperature is above the
current value. The value of the counter is loaded into a read-only register (Thermal
Sensor Thermometer Read) when the comparator first trips.
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