Variable Speed Fan. Intel AT80571RG0601ML, AT80571RG0561ML

Boxed Processor Specifications

7.4.2

Variable Speed Fan

If the boxed processor fan heatsink 4-pin connector is connected to a 3-pin motherboard header it will operate as follows:

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 cooler then lower set point. These set points, represented in

Figure 26 and

Table 30 , 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.

The motherboard must supply a constant +12 V to the processor's power header to ensure proper operation of the variable speed fan for the boxed processor. Refer to

Table 29

for the specific requirements.

Figure 26.

Boxed Processor Fan Heatsink Set Points

Higher Set Point

Highest Noise Level

Increasing Fan

Speed & Noise

Lower Set Point

Lowest Noise Level

X Y

Internal Chassis Temperature (Degrees C)

Z

Datasheet 97

Boxed Processor Specifications

Table 30.

Fan Heatsink Power and Signal Specifications

Boxed Processor

Fan Heatsink Set

Point (°C)

Boxed Processor Fan Speed

X ≤ 30

Y = 35

When the internal chassis temperature is below or equal to this set point, the fan operates at its lowest speed.

Recommended maximum internal chassis temperature for nominal operating environment.

When the internal chassis temperature is at this point, the fan operates between its lowest and highest speeds.

Recommended maximum internal chassis temperature for worst-case operating environment.

Z ≥ 38

When the internal chassis temperature is above or equal to this set point, the fan operates at its highest speed.

NOTES:

1. Set point variance is approximately ± 1 °C from fan heatsink to fan heatsink.

Notes

1

-

-

If the boxed processor fan heatsink 4-pin connector is connected to a 4-pin motherboard header and the motherboard is designed with a fan speed controller with

PWM output (CONTROL see

Table 29 ) and remote thermal diode measurement

capability the boxed processor will operate as follows:

As processor power has increased the required thermal solutions have generated increasingly more noise. Intel has added an option to the boxed processor that allows system integrators to have a quieter system in the most common usage.

The 4th wire PWM solution provides better control over chassis acoustics. This is achieved by more accurate measurement of processor die temperature through the processor's Digital Thermal Sensors (DTS) and PECI. Fan RPM is modulated through the use of an ASIC located on the motherboard that sends out a PWM control signal to the

4th pin of the connector labeled as CONTROL. The fan speed is based on actual processor temperature instead of internal ambient chassis temperatures.

If the new 4-pin active fan heat sink solution is connected to an older 3-pin baseboard processor fan header, it will default back to a thermistor controlled mode, allowing compatibility with existing 3-pin baseboard designs. Under thermistor controlled mode, the fan RPM is automatically varied based on the Tinlet temperature measured by a thermistor located at the fan inlet.

For more details on specific motherboard requirements for 4-wire based fan speed control, refer to the appropriate Thermal and Mechanical Design Guidelines (see

Section 1.2

).

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98 Datasheet