Frequency And Voltage Ordering - Intel X3350 - Xeon 2.66 Ghz 12M L2 Cache 1333MHz FSB LGA775 Quad-Core Processor Design Manual

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
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
illustration of this ordering.
Figure 6-9.

Frequency and Voltage Ordering

VIDf VIDf
VIDf VIDf
VIDf VIDf
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Intel Xeon Processor C5500/C3500 Series and LGA1366 Socket
Thermal/Mechanical Design Guide
49
f f
MAX MAX
f f
1 1
f f
2 2
MAX MAX
1 1
2 2
Temperature Temperature
Frequency Frequency
VID VID
PROCHOT# PROCHOT#
Thermal Specifications
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Xeon
Figure 6-9 for an
August 2010
Order Number: 323107-002US