Intel Pentium D 940 HH80553PG0884M ユーザーズマニュアル
製品コード
HH80553PG0884M
Thermal Specifications and Design Considerations
86
Datasheet
periods of TCC activation is expected to be so minor that it would be immeasurable. An
under-designed thermal solution that is not able to prevent excessive activation of the
TCC in the anticipated ambient environment may cause a noticeable performance loss,
and in some cases may result in a T
C
that exceeds the specified maximum temperature
and may affect the long-term reliability of the processor. In addition, a thermal solution
that is significantly under-designed may not be capable of cooling the processor even
when the TCC is active continuously. Refer to the Intel
®
Pentium
®
D Processor, Intel
®
Pentium
®
Processor Extreme Edition, and Intel
®
Pentium
®
4 Processor Thermal and
Mechanical Design Guidelines for information on designing a thermal solution.
The duty cycle for the TCC, when activated by the Thermal Monitor, is factory
configured and cannot be modified. The Thermal Monitor does not require any
additional hardware, software drivers, or interrupt handling routines.
5.2.2
On-Demand Mode
The processor provides an auxiliary mechanism that allows system software to force
the processor to reduce its power consumption. This mechanism is referred to as “On-
Demand” mode and is distinct from the Thermal Monitor feature. On-Demand mode is
intended as a means to reduce system level power consumption. Systems using the
processor must not rely on software usage of this mechanism to limit the processor
temperature.
If bit 4 of the ACPI P_CNT Control Register (located in the processor
IA32_THERM_CONTROL MSR) is written to a '1', the processor will immediately reduce
its power consumption via modulation (starting and stopping) of the internal core clock,
independent of the processor temperature. When using On-Demand mode, the duty
cycle of the clock modulation is programmable via bits 3:1 of the same ACPI P_CNT
Control Register. In On-Demand mode, the duty cycle can be programmed from 12.5%
on/87.5% off, to 87.5% on/12.5% off in 12.5% increments. On-Demand mode may be
used in conjunction with the Thermal Monitor. If the system tries to enable On-Demand
mode at the same time the TCC is engaged, the factory configured duty cycle of the
TCC will override the duty cycle selected by the On-Demand mode.
5.2.3
PROCHOT# Signal
An external signal, PROCHOT# (processor hot), is asserted when the processor core
temperature has reached its maximum operating temperature. If the Thermal Monitor
is enabled (note that the Thermal Monitor must be enabled for the processor to be
operating within specification), the TCC will be active when PROCHOT# is asserted. The
processor can be configured to generate an interrupt upon the assertion or de-
assertion of PROCHOT#. Refer to the Intel Architecture Software Developer's Manuals
for specific register and programming details.
PROCHOT# can be configured via BIOS as an output or a bi-directional signal. As an
output, PROCHOT# (Processor Hot) will go active when the processor temperature
monitoring sensor detects that one or both cores has reached its maximum safe
operating temperature. This indicates that the processor Thermal Control Circuit (TCC)
has been activated, if enabled. As an input, assertion of PROCHOT# by the system will
activate the TCC, if enabled, for both cores. The TCC will remain active until the system
de-asserts PROCHOT#.
If PROCHOT# is configured as an output only, the FORCEPR# signal can be driven from
an external source to activate the TCC. This will prevent one core from asserting the
PROCHOT# signal of the other core and unnecessarily activating the TCC of that core.
for details on the FORCEPR# signal.