Thermal Solutions
38
Intel® Xeon® Processor E5-2400 Product Family
Thermal/Mechanical Design Guide
5.6.1
T
CONTROL
and DTS Relationship
Improved acoustics and lower fan power can be achieved by understanding the
T
CONTROL
and DTS relationship, and implementing fan speed control accordingly.
5.6.1.1
Sign Convention and Temperature Filtering
Digital Thermal Sensor (DTS) and Tcontrol are relative die temperatures offset below
the Thermal Control Circuit (TCC) activation temperature. As such, negative sign
conventions are understood. While DTS and Tcontrol are available over PECI and MSR,
use of these values in fan speed control algorithms requires close attention to sign
convention. See
for the sign convention of various sources.
Where a positive (+) sign convention is shown in
, no sign bit is actually
assigned, so writers of firmware code may mistakenly assign a positive sign convention
in firmware equations. As appropriate, a negative sign should be introduced.
Where a negative (-) sign convention is shown in
firmware code will read a negative sign convention in firmware equations, as desired.
DTS obtained thru MSR (PACKAGE_THERM_STATUS) is an instantaneous value. As
such, temperature readings over short time intervals may vary considerably using this
MSR. For this reason, DTS obtained thru PECI GetTemp() may be preferred since
temperature filtering will provide the thermal trend.
5.6.1.2
Tcontrol Relief
Factory configured T
CONTROL
values are available in the appropriate Dear Customer
Letter or may be extracted by issuing a Mailbox or an RDMSR instruction. See the
appropriate External Design Specification (EDS) for more information.
Due to increased thermal headroom based on thermal characterization on the latest
processors, customers have the option to reduce T
CONTROL
to values lower than the
factory configured values.
In some situations, use of T
CONTROL
Relief can reduce average fan power and improve
acoustics. There are no plans to change Intel's specification or the factory configured
T
CONTROL
values on individual processors.
Table 5-3.
T
CONTROL
and DTS Relationship
Condition
Fan Speed Control
DTS
≤
T
CONTROL
Adjust fan speed to maintain DTS
≤
T
CONTROL
.
DTS
>
T
CONTROL
Adjust fan speed to keep T
CASE
at or below the T
CASE
based thermal profile in the
EDS, or adjust fan speed to keep DTS at or below the DTS based thermal profile in
the EDS.
Table 5-4.
Sign Convention
MSR (BWG)
PECI (EDS)
DTS
(+) using
PACKAGE_THERM_STATUS (22:16,
Digital Readout)
(-) using GetTemp()
T
CONTROL
(+) using TEMPERATURE_TARGET
(15:8, Temperature Control Offset)
(+) using Temperature Target Read
from RdPkgConfig()
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