User Guide CC9-SAMBA •
CompactPCI®
Pentium M CPU Board
© EKF -24- ekf.com
Thermal Considerations
In order to avoid malfunctioning of the CC9-SAMBA, 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. Please note, that the processors temperature is steadily measured by a special
controller (MAX1617), attached to the onboard SMBus
®
(System Management Bus). A second sensor
internal to the MAX1617 allows for acquisition of the boards surface temperature. A suitable software
to display both, the die temperature as well as the board temperature, is MBM (Motherboard
Monitor), which can be downloaded from the web. After installation, both temperatures can be
observed permanently from the Windows taskbar.
The CC9-SAMBA is equipped with a passive heatsink. Its height takes into account the 4HP limitation
in mounting space of a CPCI board. In addition, a forced vertical airflow through the system enclosure
(e.g. bottom mount fan unit) is strongly recommended (>15m
3
/h or 200LFM around the CPU slot).
As an exception, the CC9-1-SAMBA (ULV Celeron M 600MHz) can be operated with natural
convection only. 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 400 or 600LFM.
The tables 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 Pentium M 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 in up to 8 steps
down to 600MHz. This leads to an obvious reduction of power consumption (max. 6W @600MHz)
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.
A similar feature is embedded within the Graphics and Memory Controller (GMCH) i855GME. An on-
die temperature sensor is used to protect the GMCH from exceeding its maximum junction
temperature (T
J,max
=110°C) by reducing the memory bandwidth.
These features are controllable by BIOS menu entries. By default the BIOS of the CC9-SAMBA enables
mode TM2 which is the most efficient. The following diagram shows exemplary on a CC9-SAMBA
with 1.4GHz Dothan® processor the differences between the thermal modes when the board is
applied to high ambient temperatures. The performance (processor and memory scores) was
measured with the benchmark 'PCMark2002' on a Windows 2000/SP4 platform (device under test was
a CC9-3R-SAMBA with 512MB PC2700 DDR SDRAM, airflow approx. 500LFM).
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