Intel 2 Quad Q8400S BX80580Q8400S Data Sheet

Datasheet

83

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.

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. 

An external signal, PROCHOT# (processor hot), is asserted when the processor core 

temperature has reached its maximum operating temperature. If the Thermal Monitor 

is enabled (note that the Thermal Monitor must be enabled for the processor to be 

VID

Frequency

Temperature

T

TM2

f

MAX

f

TM2

VID

VID

TM2

PROCHOT#