Intel® Server Board S2600CW Family TPS
Intel® Server Board S2600CW Platform Management
Revision 2.4
81
5.3.14.6.2
Memory Thermal Management
The system memory is the most complex subsystem to thermally manage as it requires
substantial interactions between the BMC, BIOS, and the embedded memory controller HW.
This section provides an overview of this management capability from a BMC perspective.
5.3.14.6.2.1
Memory Thermal Throttling
The system only supports thermal management through closed loop throttling (CLTT)
Throttling levels are changed dynamically to cap throttling based on memory and system
thermal conditions as determined by the system and DIMM power and thermal parameters.
The BMC fan speed control functionality is related to the memory throttling mechanism used.
The following terminology is used for the various memory throttling options:
Static Closed Loop Thermal Throttling (Static-CLTT):
CLTT control registers are
configured by BIOS MRC during POST. The memory throttling is run as a closed-loop
system with the DIMM temperature sensors as the control input. Otherwise, the system
does not change any of the throttling control registers in the embedded memory
controller during runtime.
Dynamic Closed Loop Thermal Throttling (Dynamic-CLTT):
CLTT control registers are
configured by BIOS MRC during POST. The memory throttling is run as a closed-loop
system with the DIMM temperature sensors as the control input. Adjustments are
made to the throttling during runtime based on changes in system cooling (fan speed).
Intel® Server Systems supporting the Intel® Xeon® processor E5-2600 v3 and v4 product
families introduce a new type of CLTT which is referred to as Hybrid CTLL for which the
integrated Memory controller estimates the DRAM temperature in between actual reads of the
TSODs. Hybrid CLTT shall be used on all Intel® Server Systems supporting the Intel® Xeon®
processors E5-2600 v3 or v4 product family that have DIMMs with thermal sensors. Therefore,
the terms Dynamic-CLTT and Static-CLTT are really referring to this “hybrid” mode. Note that
if the IMC’s polling of the TSODs is interrupted, the temperature readings that the BMC gets
from the IMC shall be these estimated values.
5.3.14.6.3
DIMM Temperature Sensor Input to Fan Speed Control
A clamp algorithm is used for controlling fan speed based on DIMM temperatures. Aggregate
DIMM temperature margin sensors are used as the control input to the algorithm.
5.3.14.6.4
Dynamic (Hybrid) CLTT
The system will support dynamic (memory) CLTT for which the BMC FW dynamically modifies
thermal offset registers in the IMC during runtime based on changes in system cooling (fan
speed). For static CLTT, a fixed offset value is applied to the TSOD reading to get the die
temperature; however this does not provide as accurate results as when the offset takes into
account the current airflow over the DIMM, as is done with dynamic CLTT.
