Datasheet

Low Power Features
Datasheet 17
2.3 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 glitch free
transitions.
• Low transition latency and large number of transitions possible per second:
⎯ Processor core (including L2 cache) is unavailable for up to 10 μs during the
frequency transition.
— The bus protocol (BNR# mechanism) is used to block snooping.
• Improved Intel
®
Thermal Monitor mode:
⎯ When the on-die thermal sensor indicates that the die temperature is too high,
the processor can automatically perform a transition to a lower frequency and
voltage specified in a software programmable MSR.
⎯ The processor waits for a fixed time period. If the die temperature is down to
acceptable levels, an up transition to the previous frequency and voltage point
occurs.
⎯ An interrupt is generated for the up and down Intel Thermal Monitor
transitions enabling better system level thermal management.
• Enhanced thermal management features:
⎯ Digital Thermal Sensor and Out of Specification detection
⎯ Intel Thermal Monitor-1 in addition to Intel Thermal Monitor-2 in case of
unsuccessful Intel Thermal Monitor-2 transition.