On-Demand Mode; Thermal Monitor 2 Frequency And Voltage Ordering - Intel Q9300 - Core 2 Quad 2.5 GHz 6M L2 Cache 1333MHz FSB LGA775 Quad-Core Processor Datasheet

Thermal Specifications and Design Considerations
Figure 5-6.

Thermal Monitor 2 Frequency and Voltage Ordering

T
TM2
f
MAX
f
TM2
VID
VID
TM2
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.
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.
Datasheet
Temperature
Frequency
VID
PROCHOT#
83