EC FW - DTS

Introduction and Operating Principle of Digital Thermal Sensor (DTS)

The Digital Thermal Sensor (DTS) was first used in Intel's dual-core processor architecture. Because each core can operate independently or pause, the overall CPU chip temperature varies depending on the operating status of each core. To more accurately monitor and manage temperature, Intel designed DTS to provide real-time temperature information for each core to the system BIOS.

When the CPU temperature reaches a certain threshold, DTS will...SMI（System Management Interrupt）An interrupt is triggered, notifying the system BIOS. The SMI interrupt service routine in the BIOS is then called, which reads the real-time temperature of each core and sets the next upper and lower temperature thresholds.

Introduction and Operating Principle of Digital Thermal Sensor (DTS)

Digital Thermal Sensor（DTS）Originally used in Intel's dual-core processor architecture. Because each core can execute or pause independently, the overall CPU chip temperature varies depending on the operating status of each core. To more accurately monitor and manage temperature, Intel designed DTS to provide real-time temperature information for each core to the system BIOS.

When the CPU temperature reaches a certain threshold, DTS will...SMI（System Management Interrupt）An interrupt is triggered, notifying the system BIOS. The SMI interrupt service routine in the BIOS is then called, which reads the real-time temperature of each core.

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DTS operation process:

1. Booting up phase:
   The system BIOS reads the threshold value for each temperature rise/fall corresponding to DTS from the EC RAM.

2. Temperature change triggers:
   When the CPU core temperature changes, DTS triggers an SMI interrupt, and the BIOS obtains the temperature information of each core via the interrupt service routine. It then sets the upper and lower temperature limits for the next stage.

3. Compare temperature with limit values:
   The BIOS compares the highest temperature among multiple cores with the limit set by DTS.

4. Corresponding Thermal Table processing:
   If the temperature is above or below a certain limit, the BIOS will determine the corresponding control level based on the Thermal Table.

5. Fan control:
   The BIOS transmits the corresponding order to the EC (embedded controller), which then controls the fan speed or the behavior of other heat dissipation devices to achieve the effect of heat dissipation regulation. 

EC Firmware works in conjunction with BIOS to handle DTS temperature flow.

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User experience and design response

Despite Intel's designDigital Thermal Sensor (DTS)It can monitor the temperature of each core in real time and notify the BIOS via SMI, but it still has an important limitation:

When the CPU temperature exceeds itsCritical point(For example:TJ100 = 99℃、TJ85 = 84℃)hour,DTS will no longer update or report temperature changes.It will no longer notify the BIOS.

To avoid the system overheating and failing to adjust the heat dissipation strategy in a timely manner,The embedded controller (EC) still needs to obtain the actual CPU temperature through an external thermal digitizer.When an excessively high temperature is detected, the EC (Electronic Control Unit) is responsible for initiating a frequency reduction mechanism or shutting down the system to protect its safety.

1. Initialization phase:

• After powering on, the EC will set the preset...Thermal TableMoved to EC RAM.

• The system BIOS can read the Thermal Table through the standard interface (I/O Port 62h/66h) and set it in the CPU's DTS-related temporary register.

2. DTS Temperature Trigger:

• DTS will be triggered when the CPU temperature exceeds or falls below the critical threshold defined in the Thermal Table.SMI interruption。

• The BIOS's SMI handler reads the current CPU's DTS temperature and compares it with the Thermal Table to determine the new temperature level.

3. Transmission and control:

• The BIOS sends the new order back to the EC.

• EC will be compared with the previously recorded order:

• If the new order is high, it indicates an increase in temperature, and the EC will treat this order as the current control value.

• If the new order is lower, it means the temperature is lower, and the EC will be adjusted accordingly.

• However, the adjustments here are limited to the values ​​provided by DTS, and further verification of the actual temperature is still needed.

4. Temperature comparison and fan control:

• EC willDTS TemperatureCompare with the temperature from the **Remote Thermal Diode (external thermal sensor)**:

• If the temperature is within a reasonable error range, use DTS data to control the fan speed.

• If the DTS data is significantly inaccurate (e.g., it has reached the TJ limit and has not been updated), then the temperature value provided by the Remote Thermal Diode will be used for fan control instead.

In actual operation, it is frequently observed that Intel DTS fails to trigger fan speed adjustments in a timely manner when temperature changes (rise/fall), resulting in abnormally high overall system temperatures. To enhance reliability,EC Firmware employs a dual authentication mechanism of DTS and Remote Thermal Diode.This allows for more accurate CPU temperature information, enabling effective fan control and ensuring system stability and security.