Intel E5400 AT80571PG0682ML Data Sheet

Datasheet

79

periods of TCC activation is expected to be so minor that it would be immeasurable. An 

under-designed thermal solution that is not able to prevent excessive activation of the 

TCC in the anticipated ambient environment may cause a noticeable performance loss, 

and in some cases may result in a T

C

 that exceeds the specified maximum temperature 

and may affect the long-term reliability of the processor. In addition, a thermal solution 

that is significantly under-designed may not be capable of cooling the processor even 

when the TCC is active continuously. Refer to the appropriate Thermal and Mechanical 

Design Guidelines (see 

) for information on designing a thermal solution.

The duty cycle for the TCC, when activated by the Thermal Monitor, is factory 

configured and cannot be modified. The Thermal Monitor does not require any 

additional hardware, software drivers, or interrupt handling routines.

The processor also supports an additional power reduction capability known as Thermal 

Monitor 2. This mechanism provides an efficient means for limiting the processor 

temperature by reducing the power consumption within the processor. 

When Thermal Monitor 2 is enabled, and a high temperature situation is detected, the 

Thermal Control Circuit (TCC) will be activated. The TCC causes the processor to adjust 

its operating frequency (using the bus multiplier) and input voltage (using the VID 

signals). This combination of reduced frequency and VID results in a reduction to the 

processor power consumption.

A processor enabled for Thermal Monitor 2 includes two operating points, each 

consisting of a specific operating frequency and voltage. The first operating point 

represents the normal operating condition for the processor. Under this condition, the 

core-frequency-to-FSB multiple used by the processor is that contained in the 

CLK_GEYSIII_STAT MSR and the VID is that specified in 

. These parameters 

represent normal system operation.

The second operating point consists of both a lower operating frequency and voltage. 

When the TCC is activated, the processor automatically transitions to the new 

frequency. This transition occurs very 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 likely be one VID table entry (see 

). 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 ensure proper operation once the processor reaches its 

normal operating frequency. Refer to 

 for an illustration of this ordering.