Guidelines

Dual-Core Intel
®
Xeon
®
Processor 7000 Sequence Thermal /Mechanical Guidelines 15
Thermal Mechanical Design
2.2 Processor Thermal Parameters and Features
2.2.1 Thermal Control Circuit and TDP
The operating thermal limits of the processor are defined by the Thermal Profile. The intent of the
Thermal Profile specification is to support acoustic noise reduction through fan speed control and
ensure the long-term reliability of the processor. This specification requires that the temperature at
the center of the processor IHS, known as (T
CASE
) remains within a certain temperature
specification. Compliance with the T
CASE
specification is required to achieve optimal operation
and long-term reliability. See Thermal Test Vehicle User’s Guide for Case Temperature definition
and measurement methods.
To ease the burden on thermal solutions, the Thermal Monitor feature and associated logic have
been integrated into the silicon of the processor. One feature of the Thermal Monitor is the Thermal
Control Circuit (TCC). When active, the TCC lowers the processor temperature by reducing the
power consumed by the processor. This is done by changing the duty cycle of the internal processor
clocks, resulting in a lower effective frequency. When active, the TCC turns the processor clocks
off and then back on with a predetermined duty cycle.
The Dual-Core Intel Xeon processor 7000 sequence also supports an enhanced TCC that works in
conjunction with the existing Thermal Monitor logic. This capability is known as Thermal Monitor
2. This improved TCC provides a more efficient means for limiting the processor temperature by
reducing the power consumption within the processor.
Note: Not all Dual-Core Intel Xeon processor 7000 sequences are capable of supporting Thermal
Monitor 2. Details on which processor frequencies support Thermal Monitor 2 are provided in the
Prescott, Nocona, and Potomac Processor BIOS Writer’s Guide.
When Thermal Monitor 2 is enabled, and a high temperature situation is detected, the enhanced
TCC will be activated. The enhanced TCC causes the processor to adjust its operating frequency
(bus-to-core multiplier) and input voltage identification (VID) value. This combination of reduced
frequency and the lowering of VID results in a reduction in processor power consumption.
PROCHOT# is designed to assert at or a few degrees higher than maximum TCASE (as specified by
the thermal profile) when dissipating TDP power, and cannot be interpreted as an indication of
processor case temperature. This temperature delta accounts for processor package, lifetime, and
manufacturing variations and attempts to ensure the Thermal Control Circuit is not activated below
maximum TCASE when dissipating TDP power. There is no defined or fixed correlation between
the PROCHOT# trip temperature, the case temperature, or the thermal diode temperature. Thermal
solutions must be designed to the processor specifications and cannot be adjusted based on
experimental measurements of TCASE, PROCHOT#, or Tdiode on random processor samples.
By taking advantage of the Thermal Monitor features, system designers may reduce thermal
solution cost by designing to the Thermal Design Power (TDP) instead of maximum power. TDP
should be used for processor thermal solution design targets. TDP is not the maximum power that
the processor can dissipate. TDP is based on measurements of processor power consumption while
running various high power applications. This data set is used to determine those applications that
are interesting from a power perspective. These applications are then evaluated in a controlled
thermal environment to determine their sensitivity to activation of the thermal control circuit. This
data set is then used to derive the TDP targets published in the processor Datasheet. The Thermal
Monitor can protect the processor in rare workload excursions above TDP. Therefore, thermal
solutions should be designed to dissipate this target power level. The relationship between TDP to
the thermal profile, and thermal management logic and thermal monitor features, is discussed in
the sections to follow.