Thermal Specifications and Design Considerations
voltage transition back to the normal system operating point. Transition of the VID code
will occur first, to insure proper operation once the processor reaches its normal
operating frequency. Refer to Figure 5-5 for an illustration of this ordering.
Figure 5-5. Thermal Monitor 2 Frequency and Voltage Ordering
TTM2
Temperature
fMAX
fTM2
Frequency
VID
VIDTM2
VID
PROCHOT#
The PROCHOT# signal is asserted when a high temperature situation is detected,
regardless of whether Thermal Monitor or Thermal Monitor 2 is enabled.
It should be noted that the Thermal Monitor 2 TCC cannot be activated via the on
demand mode. The Thermal Monitor TCC, however, can be activated through the use of
the on demand mode.
5.2.3
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.
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 and Thermal Monitor 2
features. On-Demand mode is intended as a means to reduce system level power
consumption. Systems must not rely on software usage of this mechanism to limit the
processor temperature. If bit 4 of the IA32_CLOCK_MODULATION MSR is set 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 IA32_CLOCK_MODULATION MSR. 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;
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Dual-Core Intel® Xeon® Processor 3000 Series Datasheet
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