Sun Microsystems, Inc.
Because heat is so destructive to electronic components, lowering operating temperature will increase reliabil-
ity. Sun's cooling design enables the CPUs to operate approximately 15% more efficiently.
Fans
Cooling fans in the Sun Fire X4600 server are positioned in two rows for redundancy just behind the front bezel.
They are hot-swappable, and each fan module has an LED fault indicator. The fans are accessible from the top
top of the server, which enables the fans to be accessed without interrupting system operation. Additionally, it
makes it possible to service fans by only partially removing the server from the rack. This allows all cabling to
remain in place and prevents disturbing any non-hot-swappable components.
Figure 5-2: Sun Fire X4600 Cooling Fans
Fan speed is modulated by the Service Processor with Pulse Width Modulation by an ADM 1026 sensor chip.
All fans are controlled with the same PWM frequency so they all operate at the same speed. The ADM 1026
device uses readings from thre following three sensors to control the fan speed: Front Panel Ambient
Temperature, CPU 0 Die Temperature, and CPU 1 Die Temperature. The Service Processor reads the fan
speeds and turns the fan fault LED on if the RPM is under a set threshold.
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