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Xeon™ Processor, Intel
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E7520 Chipset, Intel
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6300ESB ICH Development Kit User’s Manual
Platform Management
2.5.1 Processor Thermal Management
Each processor monitors its own core temperature and thermally manages itself when it reaches a
certain temperature. The system also uses the internal processor diode to monitor the die
temperature. The diode pins are routed to the diode input pins in the LM 93. The LM 93 can be
programmed to force the processor fans to full speed operation when it senses the processor core
temperature exceeding a specific value. In addition, the LM 93 has an on chip thermal monitor
which allows it to monitor the incoming ambient temperature. Additional processor thermal
management requires the system to communicate to the processors when the VRD reaches a
critical temperature. The VR thermal monitor asserts FORCEPR_N signal to the processor. The
thermal monitor, an LM26, is a ±3° C precision thermostat used to sense high temperature
conditions and drive a digital output active low. This circuit works as an external PROCHOT event
to further protect the processor during high current/temperature conditions. This forces the
processor to activate a thermal protection circuit that reduces the current consumption of the
processor.
2.6 System Fan Operation
The system uses both the LM 93 and the National* 87427 Super I/O to monitor and control the fans
in the system.The LM93 uses pulse width modulated (PWM) outputs that can modulate the voltage
across the fans, providing a variable duty cycle to effect a reduced DC voltage from nominal 12
VDC. The fan headers are the standard 12V, three-pin type, used in previous Servers, which
support tachometer out. The LM 93 also has four tachometer inputs that it can use to monitor the
fans that it is controlling. All fan tachometer data can be extracted from the controllers via the
SMBus. The system fan speed control circuit does not control the power supply fan. Each PWM
output has a bypass jumper that causes all fans to run at full speed and ignore the PWM control.
Each processor fan has its own dedicated PWM output and tachometer input, so each fan is
controlled and monitored independently, depending on the core temperature. The LM 93 is
dedicated to processor fan speed control and monitor, and can be programmed with temperature
limit values that allow it to speed up or idle the processor fans, depending upon the input
temperature.