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Reference Thermal Solution
Thermal and Mechanical Design Guidelines 19
4 Reference Thermal Solution
The reference component thermal solution for the (G)MCH for ATX platforms uses two
ramp retainers, a wire preload clip, and four custom MB anchors. The Intel Balanced
Technology Extended (BTX) reference design uses a Z-clip attach for the (G)MCH
heatsink. This chapter provides detailed information on operating environment
assumptions, heatsink manufacturing, and mechanical reliability requirements for the
(G)MCH.
4.1 Operating Environment
The operating environment of the (G)MCH will differ depending on system
configuration and motherboard layout. This section defines operating environment
boundary conditions that are typical for ATX and BTX form factors. The system
designer should perform analysis on the platform operating environment to assess any
impact to thermal solution selection.
4.1.1 ATX Form Factor Operating Environment
In ATX platforms, an airflow speed of 0.76 m/s [150 lfm] is assumed to be present
25 mm [1 in] in front of the heatsink air inlet side of the attached reference thermal
solution. The system integrator should note that board layout may be such that there
will not be 25mm [1in] between the processor heatsink and the (G)MCH. The potential
for increased airflow speeds may be realized by ensuring that airflow from the
processor heatsink fan exhausts in the direction of the (G)MCH heatsink. This can be
achieved by using a heatsink providing omni directional airflow, such as a radial fin or
“X” pattern heatsink. Such heatsinks can deliver airflow to both the (G)MCH and other
areas like the voltage regulator, as shown in
Figure 5. In addition, the (G)MCH board
placement should ensure that the (G)MCH heatsink is within the air exhaust area of
the processor heatsink.
Note that heatsink orientation alone does not ensure that 0.76 m/s [150 lfm]
airflow speed will be achieved. The system integrator should use analytical or
experimental means to determine whether a system design provides adequate airflow
speed for a particular (G)MCH heatsink.
The local ambient air temperature, T
A
, at the (G)MCH heatsink in an ATX platform is
assumed to be 47 °C. The thermal designer must carefully select the location to
measure airflow to get a representative sampling. These environmental assumptions
are based on a 35 °C system external temperature measured at sea level.