Datasheet

Intel® Xeon® Processor 3500 Series Datasheet Volume 1 97
Features
7.5 Enhanced Intel SpeedStep
®
Technology
The processor features Enhanced Intel SpeedStep
®
Technology. Following are the key
features of Enhanced Intel SpeedStep Technology:
• Multiple voltage and frequency operating points provide optimal performance at the
lowest power.
• Voltage and frequency selection is software controlled by writing to processor
MSRs:
— If the target frequency is higher than the current frequency, V
CC
is ramped up
in steps by placing new values on the VID pins and the PLL then locks to the
new frequency.
— If the target frequency is lower than the current frequency, the PLL locks to the
new frequency and the V
CC
is changed through the VID pin mechanism.
— Software transitions are accepted at any time. If a previous transition is in
progress, the new transition is deferred until the previous transition completes.
• The processor controls voltage ramp rates internally to ensure smooth transitions.
• Low transition latency and large number of transitions possible per second:
— Processor core (including shared cache) is unavailable for less than 5 µs during
the frequency transition.
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