Intel 945P Benutzerhandbuch

Thermal and Mechanical Design Guidelines   

 19 

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. 

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. 

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.  

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.