Memory Open And Closed Loop Thermal Throttling; Fan Speed Control - Intel BB5520UR Technical Product Specification

Platform Management
4.3.1

Memory Open and Closed Loop Thermal Throttling

Open-Loop Thermal Throttling (OLTT)
Throttling is a solution to cool the DIMMs by reducing memory traffic allowed on the memory
bus, which reduces power consumption and thermal output. With OLTT, the system throttles in
response to memory bandwidth demands instead of actual memory temperature. Since there is
no direct temperature feedback from the DDR3 DIMMs, the throttling behavior is preset rather
than conservatively based on the worst cooling conditions (for example, high inlet temperature
and low fan speeds). Additionally, the fans that provide cooling to the memory region are also
set to conservative settings (for example, higher minimal fan speed). OLTT produces a slightly
louder system than CLTT because minimal fan speeds must be set high enough to support any
DDR3 DIMMs in the worst memory cooling conditions.
Closed-Loop Thermal Throttling (CLTT)
CLTT works by throttling the DDR3 DIMMs response directly to memory temperature via
thermal sensors integrated on the Serial Presence Detect (SPD) of the DDR3 DIMMs. This is
the preferred throttling method because this approach lowers limitations on both memory power
and thermal threshold, therefore minimizing throttling impact on memory performance. This
reduces the utilization of high fan speeds because CLTT does not have to accommodate for the
worst memory cooling conditions; with a higher thermal threshold, CLTT enables memory
performance to achieve optimal levels.
4.3.2

Fan Speed Control

BIOS and BMC software work cooperatively to implement system thermal management support.
During normal system operation, the BMC will retrieve information from the BIOS and monitor
several platform thermal sensors to determine the required fan speeds.
In order to provide the proper fan speed control for a given system configuration, the BMC must
have the appropriate platform data programmed. Platform configuration data is programmed
using the FRUSDR utility during the system integration process and by System BIOS during run
time.
4.3.2.1 System Configuration Using the FRUSDR Utility
The Field Replaceable Unit and Sensor Data Record Update Utility (FRUSDR utility) is a
program used to write platform-specific configuration data to NVRAM on the server board. It
allows the user to select which supported chassis (Intel or Non-Intel) and platform chassis
configuration is used. Based on the input provided, the FRUSDR writes sensor data specific to
the configuration to NVRAM for the BMC controller to read each time the system is powered on.
4.3.2.2 Fan Speed Control from BMC and BIOS Inputs
Using the data programmed to NVRAM by the FRUSDR utility, the BMC is configured to monitor
and control the appropriate platform sensors and system fans each time the system is powered
on. After power-on, the BMC uses additional data provided to it by the System BIOS to
determine how to control the system fans.
The BIOS provides data to the BMC telling it which fan profile the platform is set up for:
Acoustics Mode or Performance Mode. The BIOS uses the parameters retrieved from the
thermal sensor data records (SDR), fan profile setting from BIOS Setup, and altitude setting
from the BIOS Setup to configure the system for memory throttling and fan speed control. If the
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Intel® Server Boards S5520HC, S5500HCV, and S5520HCT TPS
Intel order number E39529-013
Revision 1.8