Temperature Trip Point

The internal thermal sensor reports three trip points: Cool, Hot, and Catastrophic trip points in the order of increasing temperature.

Crossing the cool trip point when going from higher to lower temperature may generate an interrupt. Crossing the hot trip point going from lower to higher temp may generate an interrupt. Each trip point has control register bits to select what type of interrupt is generated.

Crossing the cool trip point while going from low to higher temperature or crossing the hot trip point while going from high to lower temperature will not cause an interrupt.

When triggered, the catastrophic trip point will transition the system to S5 unconditionally. The register below is used to enable catastrophic assertion into S5 state. This bit should always be set in all functional cases.

The thermal alert provides built in hysteresis, by having both a high and a low mark. An example of how it works is explained below:

• Both high and low marks are programmed to their correct values
  • Assume, for an example, the high value is 90°C, and the low value is 80°C.
• TS is enabled, and assume temperature is at ambient (50°C)
  • Thus the alert signal is de-asserted.
• Temperature starts to rise as traffic flows through PCH
• Temperature reaches greater than 90°C
  • Alert signal is asserted.
  • Based on programming, a platform indication like SMI, or SCI can occur if SW had enabled such.
• Temperature reaches 95°C
  • Alert signal remains asserted.
• Temperature starts to fall and reaches 85°C
  • Alert signal remains asserted because it has not reached less than 80°C, which is the value to turn off alert.
• Temperature falls to less than 80°C
  • Alert is turned off now since the temperature has fallen to the low value.
  • Based on programming a platform indication like SMI, or SCI can occur if SW had enabled such.
• Temperature starts rising again and goes up to 85°C
  • Alert remains off until temperature rises to the high mark of greater than 90°C.

An example of how SW can use the hysteresis would be to program a value for when the fans should be turned up, or cooling should be increased (90°C in example above), then allow the cooling to be sufficient that the extra cooling can be reduced (80°C). This prevents the PCH from oscillating around one temperature with the fans increasing/decreasing every few seconds. Using the hysteresis allows the fans to be on or off for much longer periods.