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Thermal Specifications and Design Considerations—Intel
GHz
Likewise, when Intel Thermal Monitor 2 is enabled, and a high temperature situation
exists, the processor performs an voltage/frequency transition to a lower operating
point. When the processor temperature drops below the critical level, the processor
makes an voltage/frequency transition to the last requested operating point.
Note:
The Intel
frequency transitions. Intel
Enhanced Intel
or MSR based EIST transitions.
Likewise, when TM1 is enabled, and a high temperature situation exists, the clocks are
modulated by alternately turning the clocks off and on at a 50% duty cycle (automatic
mode). Cycle times are processor speed dependent and decreases linearly as processor
core frequencies increase. Once the temperature has returned to a non-critical level,
modulation ceases and TCC goes inactive. A small amount of hysteresis has been
included to prevent rapid active/inactive transitions of the TCC when the processor
temperature is near the trip point. The duty cycle is factory configured and cannot be
modified. Also, automatic mode does not require any additional hardware, software
drivers, or interrupt handling routines. Processor performance is decreased by the
same amount as the duty cycle when the TCC is active.
The TCC may also be activated via on-demand mode. If bit 4 of the ACPI Intel Thermal
Monitor control register is written to a 1, the TCC is activated immediately, independent
of the processor temperature. When using on-demand mode to activate the TCC, the
duty cycle of the clock modulation is programmable via bits 3:1 of the same ACPI Intel
Thermal Monitor control register. In automatic mode, the duty cycle is fixed at 50% on,
50% off, however 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 at the same time automatic mode is enabled, however, if the system tries to
enable the TCC via on-demand mode at the same time automatic mode is enabled and
a high temperature condition exists, automatic mode takes precedence
An external signal, PROCHOT# (processor hot) is asserted when the processor detects
that its temperature is above the thermal trip point. Bus snooping and interrupt
latching are also active while the TCC is active.
Besides the thermal sensor and thermal control circuit, the Intel Thermal Monitor also
includes one ACPI register, one performance counter register, three model specific
registers (MSR), one output pin (PROCHOT#), and one input pin (FORCEPR#). All are
available to monitor and control the state of the Intel thermal monitor feature. The
Intel thermal monitor can be configured to generate an interrupt upon the assertion or
deassertion of PROCHOT#.
Note:
PROCHOT# is not asserted when the processor is in the Stop Grant, and Sleep, low
power states (internal clocks stopped), hence the thermal diode reading must be used
as a safeguard to maintain the processor junction temperature within maximum
specification. If the platform thermal solution is not able to maintain the processor
junction temperature within the maximum specification, the system must initiate an
orderly shutdown to prevent damage. If the processor enters a low power state with
PROCHOT# already asserted, PROCHOT# remains asserted until the processor exits
the low power state and the processor junction temperature drops below the thermal
trip point.
If Thermal Monitor automatic mode is disabled, the processor is operating out of
specification. Regardless of enabling the automatic or on-demand modes, in the event
of a catastrophic cooling failure, the processor automatically shuts down when the
silicon has reached a temperature of approximately 125 °C. At this point the
THERMTRIP# signal goes active. THERMTRIP# activation is independent of processor
activity and does not generate any bus cycles. When THERMTRIP# is asserted, the
processor core voltage must be shut down within the time specified in
January 2007
Order Number: 315876-002
®
®
Celeron
Processor 1.66 GHz/1.83 GHz only supports TM2 initiated voltage/
®
Celeron
®
®
SpeedStep
Technology (EIST) therefore it does not support software
®
®
Celeron
Processor 1.66 GHz/1.83
®
Processor 1.66 GHz/1.83 GHz does not support
®
Intel
Celeron
Chapter
3.0.
®
Processor 1.66 GHz/1.83 GHz
DS
65
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