Intel 4 515/515J JM80547PE0771M User Manual

Product codes
JM80547PE0771M
Page of 96
 
Datasheet
81
Thermal Specifications and Design Considerations
The PROCHOT# signal is asserted when a high temperature situation is detected, regardless of 
whether or not Thermal Monitor or Thermal Monitor 2 is enabled.
It should be noted that the Thermal Monitor 2 TCC can not 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 Pentium 4 processor in the 775-land package 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 in the 775-land package 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 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 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. 
Figure 5-4. Thermal Monitor 2 Frequency and Voltage Ordering
VID
Frequency
Temperature
T
TM2
f
MAX
f
TM2
VID
VID
TM2
PROCHOT#
Time