Intel Xeon, 6300ESB ICH user manual System Fan Operation, Processor Thermal Management

Platform Management

2.5.1Processor 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.

2.6System 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.

16Intel® Xeon™ Processor, Intel® E7520 Chipset, Intel® 6300ESB ICH Development Kit User’s Manual