64-bit Intel Xeon Processor with 2MB L2 Cache Thermal/Mechanical Design Guidelines

Processor Thermal Management Logic and Thermal Monitor Features
72 64-bit Intel® Xeon™ Processor with 2MB L2 Cache Thermal/Mechanical Design Guidelines
Cache Versions) Specification Update when available. For more details also refer to IA-32 Intel
®
Architecture Software Developer's Manual Volume 3: System Programming 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.
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. 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 microseconds). During the frequency transition,
the processor is unable to service any bus requests, and consequently, all bus traffic is blocked
during the frequency transition. 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 changes 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 be one VID table entry (i.e. 12.5 mV steps). The processor continues to execute
instructions during the voltage transition. Operation at the lower voltage reduces both the dynamic
and leakage power consumption of the processor. Once the processor has sufficiently cooled, and
the time based hysteresis period 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 insure
proper operation once the processor reaches its normal operating frequency. Refer to Figure E-3 for
an illustration of this ordering.
Figure E-3. Thermal Monitor 2 Frequency and Voltage Ordering