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Thermal Specifications and Design Considerations

Dual-Core Intel® Xeon® Processor 3000 Series Datasheet

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.

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;

Figure 5-5. Thermal Monitor 2 Frequency and Voltage Ordering

VID

Frequency

Temperature

TM2

MAX

TM2

VID

TM2

PROCHOT#

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