Supermicro Xeon P4X4-028-512K User Manual

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The Processor Wind Tunnel includes a 25mm fan for use with processors <= 2.8 GHz, or a 38mm 

fan for use with processors running at 3 GHz and above. The 38mm fan provides the high 
performance required to meet the demanding thermal requirements of processors running at 3 GHz 

and above. The 38mm fan provides local fan speed control. There is a temperature diode on the fan 

that measures the inlet temperature to the fan and adjusts the speed accordingly. The benefit is that 
system manufacturers can pass acoustical requirements while still being able to pass thermal 

requirements at maximum ambient temperature. 

The 1U solution contains a passive heatsink and a foam pad, in addition to the retention solution 
included with the other options. Because of the small form factor, the 1U heatsink is not as efficient 
at dissipating heat as the general-purpose heatsink. In order to ensure maximum thermal efficiency, 
the foam pad must be attached to the top of the 1U heatsink, blocking airflow between the heatsink 
and the chassis cover. This will force air through the heatsink fins instead of allowing it to bypass 
over the top. See 

 and 

 for more detail on installation.