Boxed Processor Specifications
Figure 7-7. Boxed Processor Fan Heatsink Airspace Keep-Out Requirements (Side 2 View)
7.4.2
Variable Speed Fan
The boxed processor fan will operate at different speeds over a short range of internal chassis
temperatures. This allows the processor fan to operate at a lower speed and noise level, while
internal chassis temperatures are low. If internal chassis temperature increases beyond a lower set
point, the fan speed will rise linearly with the internal temperature until the higher set point is
reached. At that point, the fan speed is at its maximum. As fan speed increases, so does fan noise
levels. Systems should be designed to provide adequate air around the boxed processor fan
heatsink that remains below the lower set point. These set points, represented in Figure 7-8 and
Table 7-2, can vary by a few degrees from fan heatsink to fan heatsink. The internal chassis
temperature should be kept below 38 ºC. Meeting the processor’s temperature specification
(see Chapter 5) is the responsibility of the system integrator.
Figure 7-8. Boxed Processor Fan Heatsink Set Points
Higher Set Point
Highest Noise Level
Increasing Fan
Speed & Noise
Lower Set Point
Lowest Noise Level
X
Y
Z
Internal Chassis Temperature (Degrees C)
Intel® Pentium® 4 Processor on 0.13 Micron Process Datasheet
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