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

64-bit Intel® Xeon™ Processor with 2MB L2 Cache Thermal/Mechanical Design Guidelines 73
Processor Thermal Management Logic and Thermal Monitor Features
E.1.5 System Considerations
The Thermal Monitor feature may be used in a variety of ways, depending upon the system design
requirements and capabilities.
• Intel requires the TCC to be enabled for all 64-bit Intel Xeon Processor with 2MB L2
Cache-based systems. At a minimum, the TCC provides an added level of protection against
processor thermal solution failure.
A system designed to meet the TDP and T
CASE
targets published in the processor datasheet greatly
reduces the probability of real applications causing the TCC to activate under normal operating
conditions. Systems that do not meet these specifications could be subject to more frequent
activation of the TCC depending upon ambient air temperature and application power profile.
Moreover, if a system is significantly under designed, there is a risk that the Thermal Monitor
feature will not be capable of maintaining a safe operating temperature and the processor could
shutdown and signal THERMTRIP#.
For information regarding THERMTRIP#, refer to Section E.1.8.1 and to the processor datasheet.
E.1.6 Operating System and Application Software Considerations
The Thermal Monitor feature and its TCC work seamlessly with ACPI compliant operating
systems and those utilizing hardware based timing routines. The Thermal Monitor feature is
transparent to application software since the processor bus snooping, ACPI timer, and interrupts
are active at all times.
Activation of the TCC during a non-ACPI aware operating system boot process may result in
incorrect calibration of operating system software timing loops. This is also the case with operating
systems that utilize execution based timing routines. The BIOS must disable the TCC prior to boot
and then the operating system or BIOS must enable the TCC after the operating system boot
process completes. Refer to the
IA-32 Intel
®
Architecture Software Developer's Manual Volume
3: System Programming Guide
for specific programming details.
Intel has worked with the major operating system vendors to ensure support for non-execution
based operating system calibration loops and ACPI support for the Thermal Monitor feature.
E.1.7 Legacy Thermal Management Capabilities
In addition to Thermal Monitor, the 64-bit Intel Xeon Processor with 2MB L2 Cache supports the
same thermal management features originally introduced with the Intel

Pentium

III Xeon™
processor. These features include the on-die thermal diode and THERMTRIP# signal for indicating
catastrophic thermal failure.
E.1.8 On-Die Thermal Diode
There are two independent thermal diodes in the 64-bit Intel Xeon Processor with 2MB L2 Cache.
One is the on-die thermal diode and the other is in the temperature sensor used for the Thermal
Monitor and for THERMTRIP#. The Thermal Monitor’s temperature sensor and the on-die
thermal diode are independent and isolated devices with no direct correlation to one another.
Circuit constraints and performance requirements prevent the Thermal Monitor’s temperature
sensor and the on-die thermal diode from being located at the same place on the silicon. The
temperature distribution across the die may result in significant temperature differences between