Thermal Specifications and Design Considerations
Figure 15.
Thermal Monitor 2 Frequency and Voltage Ordering
TTM2
Temperature
Frequency
fMAX
fTM2
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.
Note 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
Pentium 4 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 immediately reduces 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.
Datasheet
81
INTEL [ INTEL ]
