Intel® Server System Server System "Emerald Ridge ... - CTL

錯 誤 ! 尚 未 定 義 樣 式 。 EPSFunctional Specificationwindow, the BMC does not recalculate the fan speed until the sensor reads 28º C or higher, dueto the positive hysteresis, or 23º C or lower, due to the negative hysteresis. When one of thesetemperature ranges is reached, the fan speed is recalculated and the hysteresis window is resetbased upon the new reading. See the figure below.TemperatureFigure 4. Stepwise Linear Control HysteresisThis prevents oscillating fan speed behavior, although it is different from the IPMI sensorthreshold interpretation of hysteresis, which is applied to the thresholds not to the reading.3.16.4.1.2 Domain MaximumStepwise linear Tcontrol sub-records might have a flag set that indicates that the instanceprovides the fan domain maximum PWM value. These sub-records do not contribute to the fanspeed. Instead, the fan speed obtained through the table lookup is saved for reference. Whenthe final domain contribution is calculated, it is reduced, if necessary, to this domain maximumvalue. This limits the maximum noise output of the system for a given ambient temperature toensure acoustic specifications are met.Hysteresis is not applied to domain maximum sub-records.3.16.4.2 ClampClamp Tcontrol sub-records specify one temperature value and direct the BMC to increase thefan speed for the associated fan domain as necessary to maintain the value of thecorresponding temperature sensor below the clamp value. If the sensor reading exceeds theclamp value, then the fan speed contribution increases over time until either the fan speedreaches saturation (maximum speed) or the temperature drops below the threshold. If thetemperature is below the threshold, the sensor’s contribution is reduced over time until itreaches zero. Fan speed changes occur in the step size specified in the sub-record.Revision 1.1Intel ® Confidential 31