Kontron pITX-SP - Manual (Page 41)

KTD-S0003-C Page 37 ACPI Thermal Management
p ITX-SP Software Guide
9 ACPI Thermal Management
The ACPI thermal management supports two modes: passive cooling (decrease the system performance, but
produce no noise) and active cooling (no performance loss, but noise production).
9.1 Passive Cooling
Passive cooling controls the processor temperature by activating the automatic thermal throttling after the
processor reaches a certain temperature. You can specify the temperature level when throttling starts,
define a hysteresis value to get back to full processor performance and specify the percentage for the
performance in throttling mode. This mode does not require additional drivers or programs.
9.2 Active Cooling
Only from hardware revision 4.00 on (see PCB) the fan is switched on and off mostly by the hardware. On
older boards this is realized through software. The operating system continuously polls the temperature
using the ACPI method '_TZP' (Thermal Zone Polling). This is done automatically by Linux - for Windows
®
operating systems an additional tool is needed as Windows ® ignores the ACPI method '_TZP'.
For example the tool
CPUID HWMonitor Vers. 1.14.0 or greater
can be used. From hardware revision 4.00 on no additional tool is needed for a Windows ® operating system.
This approach accounts the total control of the fan through the temperature control and the fan can not be
switched seperatly on and off by the ACPI methods. This is only possible when inside the BIOS Setup the
setting
Advanced/ACPI Configuration/ACPI Cooling Options/Active Trip Point is set to Disabled.
9.3 Temperature Limits
All three trip points have the setting Disabled. This is not a real deactivating of the trip points but the
corresponding value is set to 125°C which is the internal catastrophic temperature.
9.4 Temperature Identifier
Within operating systems (e.g. Linux) the temperature can be determined through the identifier THRM:
cat /proc/acpi/thermal_zone/ THRM/temperature