User Guide • PC3-ALLEGRO • CompactPCI
®
PlusIO CPU Board • Intel® i7-3xxx Processor
Thermal Considerations
In order to avoid malfunctioning of the PC3-ALLEGRO, take care of appropriate cooling of the processor and
system, e.g. by a cooling fan suitable to the maximum power consumption of the CPU chip actually in use. The
processor contains digital thermal sensors (DTS) that are readable via special CPU registers. DTS allows to get
the temperatures of each CPU core separately.
Two further temperature sensors, located in the system hardware monitor LM87, allows for acquisition of the
boards surface temperature and the thermal state of the onboard system memory channel. Beside this the
LM87 also monitors most of the supply voltages. A suitable software on Microsoft Windows® systems to
display both, the temperatures as well as the supply voltages, is Speedfan, which can be downloaded from the
web. After installation, both temperatures and voltages can be observed permanently from the Windows®
taskbar.
The PC3-ALLEGRO is equipped with a passive heatsink. Its height takes into account the 4HP limitation in
mounting space of a
CompactPCI
®
board. In addition, a forced vertical airflow through the system enclosure
(e.g. bottom mount fan unit) is strongly recommended (>20m
3
/h or 2m/s (400LFM) around the CPU slot). Be
sure to thoroughly discuss your actual cooling needs with EKF. Generally, the faster the CPU speed the higher
its power consumption. For higher ambient temperatures, consider increasing the forced airflow to 3m/s
(600LFM) or more.
The table showing the supported processors above give also the maximum power consumption (TDP = Thermal
Design Power) of a particular processor. Fortunately, the power consumption is by far lower when executing
typical Windows® or Linux tasks. The heat dissipation increases when e.g. rendering software like the Acrobat
Distiller is executed.
The Core
TM
i7 processors support Intel's Enhanced SpeedStep® technology. This enables dynamic switching
between multiple core voltages and frequencies depending on core temperature and currently required
performance. The processors are able to reduce their core speed and core voltage in multiple steps down to
1200MHz (800MHz for LV/ULV processors). Additional a reduction of the graphics core clock and voltage is
possible. This leads to an obvious reduction of power consumption resulting in less heating. This mode of
lowering the processor core temperature is called TM2 (TM=Thermal Monitor).
Another way to reduce power consumption is to modulate the processor clock. This mode (TM1) is achieved by
actuating the 'Stop Clock' input of the CPU. A throttling of 50% e.g. means a duty cycle of 50% on the stop
clock input. However, while saving considerable power consumption, the data throughput of the processor is
also reduced. The processor works at full speed until the core temperature reaches a critical value. Then the
processor is throttled by 50%. As soon as the high temperature situation disappears the throttling will be
disabled and the processors runs at full speed again.
These features are controllable by BIOS menu entries. By default the BIOS of the PC3-ALLEGRO enables mode
TM2 which is the most efficient.
© EKF -19- ekf.com
