Technical Product Specification

Intel® Server Boards S4600LH2/T2 TPS
Revision 2.0
70
9. Available only when PSU has PMBus*
The following illustration provides a simple model showing the fan speed control structure that implements the
resulting fan speeds.
The following illustration provides a simple model showing the fan speed control structure that implements the
resulting fan speeds.
Figure 22. Fan Speed Control Process
6.9.3 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).