Intel X3350 Design Guide - Page 49

Thermal Specifications 6.2.2.1 Frequency/VID Control The processor uses Frequency/VID control whereby TCC activation causes the processor to adjust its operating frequency (via the core ratio multiplier) and input voltage (via the VID signals). This combination of reduced frequency and VID results in a reduction to the processor power consumption. This method includes multiple operating points, each consisting of a specific operating frequency and voltage. The first operating point represents the normal operating condition for the processor. The remaining points consist of both lower operating frequencies and voltages. When the TCC is activated, the processor automatically transitions to the new operating frequency. This transition occurs very rapidly (on the order of 2 microseconds). Once the new operating frequency is engaged, the processor will transition to the new core operating voltage by issuing a new VID code to the voltage regulator. The voltage regulator must support dynamic VID steps to support this method. During the voltage change, it will be necessary to transition through multiple VID codes to reach the target operating voltage. Each step will be one VID table entry (see the Intel® Xeon® Processor C5500/C3500 Series Datsheet). The processor continues to execute instructions during the voltage transition. Operation at the lower voltages reduces the power consumption of the processor. A small amount of hysteresis has been included to prevent rapid active/inactive transitions of the TCC when the processor temperature is near its maximum operating temperature. Once the temperature has dropped below the maximum operating temperature, and the hysteresis timer has expired, the operating frequency and voltage transition back to the normal system operating point via the intermediate VID/ frequency points. Transition of the VID code will occur first, to insure proper operation once the processor reaches its normal operating frequency. Refer to Figure 6-9 for an illustration of this ordering. Figure 6-9. Frequency and Voltage Ordering Temperature fMAX f1 f2 VIDfMAX VIDf1 VIDf2 Frequency VID PROCHOT# Intel® Xeon® Processor C5500/C3500 Series and LGA1366 Socket Thermal/Mechanical Design Guide 49 August 2010 Order Number: 323107-002US