Modes of Operation

The Thermal sensors have two usages when enabled:

1. One use is to provide the temperature of the PCH in units of 1 ^oC. There is a 8 bit field for the temperature, with a theoretical range from –128 ^oC to +127 ^oC. Practically the operational range for the system is between -40 ^oC and 125 ^oC.
2. The second use is to allow programmed trip points to cause alerts to SW or in the extreme case shutdown. Temperature may be provided without having any SW alerts set.

There are two thermal alert capabilities. One is for the catastrophic event (thermal runaway) which results in an immediate system power down (S5 state). The other alert provides an indication to the platform that a particular temperature has been caused. The other alert is triggered when the temperature exceeds a predefined threshold. This second alert needs to be routed to SMI or SCI based on SW programming.

The PCH in general intends to incorporate multiple thermal sensors for various reasons. The PCH provides a direct reading of the temperature to the host software, to Intel CSME, external EC through the eSPI and any other IP on the PCH which subscribes to receive periodical temperature reporting.

The thermal sensor is operational in S0, Sx and S0ix states.

The Thermal functions working during Sx would be DTS sending periodic temperature to PCH.

The DTS will continue to read temperatures in S0ix modes. However, the frequency of the reads will be less (i.e. once every second). In S0ix mode the DTS has capability to compare the temperature with a temperature threshold (5 ^o C) programmed value. If the temperature is below the threshold then the DTS will wake up the system and send the temperature to the PCH. Else it will silently discard the temperature and will not send them to the PCH.

Typically the programmed value will be set in the range of 110 ^oC to 125 ^oC, depending on particular OEM system parameters.