Intel Xeon Processor with 800 MHz System Bus Thermal/Mechanical Design Guide

Intel® Xeon™ Processor with 800 MHz System Bus Thermal/Mechanical Design Guidelines 17
Thermal/Mechanical Reference Design
Intel Xeon Processor with 800 MHz System Bus, 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 5. 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 EMTS.
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.
The T
CONTROL_BASE
value for the Intel Xeon Processor with 800 MHz System Bus 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 2-3 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
minimum for the given processor family). Any Offset value greater than 0 moves the point where
the Thermal Profile must be met upwards, as shown by location 2 on the graph. If the diode
temperature is less than T
CONTROL
, then the case temperature is permitted to exceed the Thermal
Profile, but the diode temperature must remain at or below T
CONTROL
. In other words, there is no
T
CASE
specification for the processor at power levels less than Pcontrol. The thermal solution for
the processor must be able to keep the processor’s T
CASE
at or below the T
CASE
values defined by
the Thermal Profile between the T
CASE
MAX @T
CONTROL
and T
CASE
MAX points at the
corresponding power levels.
Refer to Chapter 2.3.1 for the implementation of the T
CONTROL
value in support of fan speed
control (FSC) design to achieve better acoustic performance.
Figure 2-3. T
CONTROL
and Thermal Profile Interaction
Pcontrol_base
TDP
T
CASE
T
CASE
MAX
T
CASE
@
Pcont rol_base
Power
Thermal Profile
T
CASE
@ T
CONT ROL
Pcont rol
1
2
Pcontrol_base
TDP
T
CASE
T
CASE
MAX
T
CASE
@
Pcont rol_base
Power
Thermal Profile
T
CASE
@ T
CONT ROL
Pcont rol
1
2
T
CASE
MAX @
T
CONTROL
T
CASE
MAX @
Pcont rol_base
T
CASE
MAX
Pcontrol_base
TDP
T
CASE
T
CASE
MAX
T
CASE
@
Pcont rol_base
Power
Thermal Profile
T
CASE
@ T
CONT ROL
Pcont rol
1
2
Pcontrol_base
TDP
T
CASE
T
CASE
MAX
T
CASE
@
Pcont rol_base
Power
Thermal Profile
T
CASE
@ T
CONT ROL
Pcont rol
1
2
T
CASE
MAX @
T
CONTROL
T
CASE
MAX @
Pcont rol_base
T
CASE
MAX