Guidelines

Thermal Mechanical Design
20 Dual-Core Intel
®
Xeon
®
Processor 7000 Sequence Thermal /Mechanical Guidelines
2.2.4 T
CONTROL
Definition
T
CONTROL
is a temperature specification based on a temperature reading from the processor’s
thermal diode. T
CONTROL
defines the lower end of the Thermal Profile line for a given processor,
and it can be described as a trigger point for fan speed control implementation. The value for
T
CONTROL
is calibrated in manufacturing and configured for each processor individually. For the
Dual-Core Intel Xeon processor 7000 sequence the Tcontrol value is obtained by reading a
processor model specific register (MSR) and adding this offset value to a base value. The equation
for calculating T
CONTROL
is:
Equation 2-2. T
CONTROL
= T
CONTROL_BASE
+ Offset
Where:
T
CONTROL_BASE
= A fixed base value defined for a given processor generation as
published in the processor Datasheet.
Offset = A value programmed into each processor during manufacturing that
can be obtained by reading the
IA32_TEMPERATURE_TARGET_MSR. This is a static and a
unique value. Refer to the Prescott, Nocona, and Potomac Processor
BIOS Writer’s Guide for further details.
The T
CONTROL_BASE
value for the Dual-Core Intel Xeon processor 7000 sequence is 50°C. The
Offset value, which depends on several factors (i.e. leakage current), can be any number between 0
and (T
CASE
MAX - T
CONTROL_BASE
). Figure 2-6 depicts the interaction between the Thermal
Profile and T
CONTROL
for an Offset value that is greater than 0 (i.e. T
CONTROL
greater than
T
CONTROL_BASE
).
Since T
CONTROL
is a processor diode temperature value, an equivalent T
CASE
temperature must be
determined to plot the T
CASE
MAX @ T
CONTROL
point on the Thermal Profile graph. Location 1
on the Thermal Profile represents a T
CASE
value corresponding to an Offset of 0 (the theoretical
Figure 2-6. T
CONTROL
and Thermal Profile Interaction