82NM10 Datasheet, PDF (148/671 Pages) Intel Corporation – Intel® NM10 Family Express Chipset

Functional Description
If the THRM_POL bit is set low, when the THRM# signal goes low, the THRM_STS bit
will be set. This is an indicator that the thermal threshold has been exceeded. If the
THRM_EN bit is set, then when THRM_STS goes active, either an SMI# or SCI will be
generated (depending on the SCI_EN bit being set).
The power management software (BIOS or ACPI) can then take measures to start
reducing the temperature. Examples include shutting off unwanted subsystems, or
halting the processor.
By setting the THRM_POL bit to high, another SMI# or SCI can optionally be generated
when the THRM# signal goes back high. This allows the software (BIOS or ACPI) to
turn off the cooling methods.
Note:
THRM# assertion does not cause a TCO event message in S3 or S4. The level of the
signal is not reported in the heartbeat message.
5.14.8.2
Processor Initiated Passive Cooling
This mode is initiated by software setting the THTL_EN (PMBASE+10h:bit 4) or
FORCE_THTL (PMBASE+10h:bit 8) bits.
Software sets the THTL_DTY (PMBASE+10h:bits 3:1) or THRM_DTY (PMBASE+10h:bits
7:5) bits to select throttle ratio and THTL_EN or FORCE_THTL bits to enable the
throttling.
Throttling results in STPCLK# active for a minimum time of 12.5% and a maximum of
87.5%. The period is 1024 PCI clocks. Thus, the STPCLK# signal can be active for as
little as 128 PCI clocks or as much as 896 PCI clocks. The actual slowdown (and
cooling) of the processor depends on the instruction stream, because the processor is
allowed to finish the current instruction. Furthermore, Chipset waits for the STOP-
GRANT cycle before starting the count of the time the STPCLK# signal is active.
5.14.8.3
THRM# Override Software Bit
The FORCE_THTL bit allows the BIOS to force passive cooling, independent of the ACPI
software (which uses the THTL_EN and THTL_DTY bits). If this bit is set, Chipset starts
throttling using the ratio in the THRM_DTY field.
When this bit is cleared Chipset stops throttling, unless the THTL_EN bit is set
(indicating that ACPI software is attempting throttling).
If both the THTL_EN and FORCE_THTL bits are set, then Chipset should use the duty
cycle defined by the THRM_DTY field, not the THTL_DTY field.
5.14.8.4
Active Cooling
Active cooling involves fans. The GPIO signals from Chipset can be used to turn on/off a
fan.
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Datasheet