rtd cpuModules CME34BT, User Manual, Page: 73 / 110

BDM-610000088 Rev A Chapter 4: Using the cpuModule 65
Thermal Management
The cpuModule has several thermal features which can be used to monitor and control the board’s
temperature when extreme operating conditions are prevalent.
Thermal Warning
The cpuModule includes a Thermal Warning mechanism which will assert a signal when the processor’s
temperature has reached or exceeded 100 C. At this time, a bit will be set in the reset and event status register
to indicate that this temperature has been entered. Although the LED has turned white and a thermal
warning bit has been set, the CPU will maintain the current power and operating state.
For more information on the reset status register, refer to
Reset and Event Status Register
—page 69.
ACPI-Enforced Thermal Protection
When the maximum thermal junction temperature of the processor is reached, the system is at risk of
malfunctioning, and the cpuModule may become permanently damaged.
For operating system with ACPI support, the system offers two mechanisms to help prevent the processor
from reaching its maximum thermal junction temperature -- the Critical Trip Point and the Passive Trip
Point . Both of these temperatures may be configured in the BIOS Setup.
Critical Trip Point
The Critical Trip Point controls the temperature at which an ACPI operating system will shut down the
system. Upon entering the Critical Trip state, the operating system will issue a command to the processor,
and the CME34BT will immediately transition to the S5 (Soft-Off) ACPI power state.
To exit the Critical Trip state (and S5), the CPU temperature must be reduced to a point that the internal
thermal sensors are below the Critical Trip Point. Next, a power cycle or RSM reset (deepest reset) is
required. The reset button may be configured as an RSM reset (default BIOS setting) in the BIOS setup
utility.
For more information on the S5 power state, refer to
Advanced Configuration and Power Interface
(ACPI)
—page 66.
Passive Trip Point
The Passive Trip Point controls the temperature at which an ACPI operating system will begin to throttle
the processor.
Further Temperature Reduction
The cpuModule’s temperature is directly related to power consumption. Reducing the power consumption
of the cpuModule will have an effect on the cpuModule’s temperature. Suggested methods for reducing the
cpuModule’s power consumption can be found in the
Power Management
section on page 66.