Avnet Qseven MSC Q7-BT - Critical shutdown; Temperature regulation using clock speed; Active cooling

MSC Q7-BT MSC_Q7-BT_User_Manual.pdf 24 / 113
2.3 Thermal Management
The MSC Q7-BT modules have a number of mechanisms for regulating over temperature conditions, these are described below :
1. Critical shutdown
If the Tcpu_junction temperature reaches 115°C (Atom E38xx), 110°C (Celeron J1900) or 105°C (Celeron N29xx) then the CPU will perform a system
shutdown.
2. Temperature regulation using clock speed
If the Tcpu_junction reaches 110°C (Atom E38xx), 105°C (Celeron J1900 ) or 100°C (Celeron N29xx) then the CPU will attempt to reduce the
temperature using two methods:
- TM1 – clock throttling – CPU clock will be stretched effectively halving the clock speed.
- TM2 – speed stepping – CPU will reduce core voltage and clock frequency to reduce temperature. Minimum frequency is 600MHz.
TM1 and TM2 cannot be altered in the BIOS setup. Speed stepping can however be disabled in BIOS setup, which effectively disables TM2.
Therefore it is recommended to not disable the speed stepping – even if the application is real time critical. In the case where real time applications
are supported the speed stepping should be configured appropriately using the power management settings in the OS (eg Windows Energy
management – Desktop, always powered, or Linux Governors) and not disabled in the BIOS.
The TM1 and TM2 mechanisms are rescue mechanisms to try and stop the CPU reaching the shutdown temperature – the system should be
designed so that they are never needed.
The TM1 and TM2 mechanisms are built into the CPU and so do not require software interaction.
3. Active cooling
There is a fan control mechanism with threshold / fan speed configuration in the BIOS setup. This mechanism is controlled by the embedded board
controller and requires no software interaction. More details on this can be seen in the BIOS section of this manual.