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rapidly, on the order of 5 µs. During the frequency transition, the processor is unable to
service any bus requests, and consequently, all bus traffic is blocked. Edge-triggered
interrupts will be latched and kept pending until the processor resumes operation at the
new frequency.
Once the new operating frequency is engaged, the processor will transition to the new
core operating voltage by issuing a new VID code to the voltage regulator. The voltage
regulator must support dynamic VID steps in order to support Thermal Monitor 2.
During the voltage change, it will be necessary to transition through multiple VID codes
to reach the target operating voltage. Each step will be one VID table entry (see
Table
2-3). The processor continues to execute instructions during the voltage
transition. Operation at the lower voltage reduces the power consumption of the
processor.
A small amount of hysteresis has been included to prevent rapid active/inactive
transitions of the TCC when the processor temperature is near its maximum operating
temperature. Once the temperature has dropped below the maximum operating
temperature, and the hysteresis timer has expired, the operating frequency and
voltage transition back to the normal system operating point. Transition of the VID code
will occur first, in order to insure proper operation once the processor reaches its
normal operating frequency. Refer to
Figure 6-7.
Thermal Monitor 2 Frequency and Voltage Ordering
T
T
TM2
TM2
f
f
MAX
MAX
f
f
TM2
TM2
V
V
NOM
NOM
V
V
TM2
TM2
The PROCHOT# signal is asserted when a high temperature situation is detected,
regardless of whether TM1 or TM2 is enabled.
6.3.4
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 1 and Thermal Monitor 2
features. On-Demand mode is intended as a means to reduce system level power
consumption. Systems utilizing the Quad-Core Intel® Xeon® Processor 5300 Series
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
100
Figure 6-7
for an illustration of this ordering.
Temperature
Temperature
Frequency
Frequency
Vcc
Vcc
Time
Time
T(hysterisis)
T(hysterisis)
Quad-Core Intel® Xeon® Processor 5300 Series Datasheet
Thermal Specifications
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