Technical Product Specification

Platform Management Functional Overview Intel
®
Server Board S2400EP TPS
Intel order number G50763-002 Revision 2.0
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Figure 25. Fan Speed Control Process
6.8.4 Memory Thermal Throttling
The server board provides support for system thermal management through open loop
throttling (OLTT) and closed loop throttling (CLTT) of system memory. Normal system operation
uses closed-loop thermal throttling (CLTT) and DIMM temperature monitoring as major factors
in overall thermal and acoustics management. In the event that BIOS is unable to configure the
system for CLTT, it defaults to open-loop thermal throttling (OLTT). In the OLTT mode, it is
assumed that the DIMM temperature sensors are not available for fan speed control.
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’s fan speed control functionality is linked to the memory throttling mechanism used.
The following terminology is used for the various memory throttling options:
 Static Open Loop Thermal Throttling (Static-OLTT): OLTT control registers that are
configured by BIOS MRC remain fixed after post. The system does not change any of the
throttling control registers in the embedded memory controller during runtime.
 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 Open Loop Thermal Throttling (Dynamic-OLTT): OLTT control registers are
configured by BIOS MRC during POST. Adjustments are made to the throttling during
runtime based on changes in system cooling (fan speed).