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Enhanced Intel SpeedStep Technology creates processor performance states (P-states)
or voltage/frequency operating points. P-states are lower power capability states within
the Normal state as shown in
enables real-time dynamic switching between frequency and voltage points. It alters
the performance of the processor by changing the bus to core frequency ratio and
voltage. This allows the processor to run at different core frequencies and voltages to
best serve the performance and power requirements of the processor and system. The
®
Intel
Xeon
coordinates the requested voltage (VID) between the processor cores. The highest
voltage requested from the four processor cores is selected for that processor package.
Note that the front side bus is not altered; only the internal core frequency is changed.
In order to run at reduced power consumption, the voltage is altered in step with the
bus ratio.
The following are key features of Enhanced Intel SpeedStep Technology:
• Multiple voltage/frequency operating points provide optimal performance at
reduced power consumption.
• Voltage/frequency selection is software controlled by writing to processor MSR's
(Model Specific Registers), thus eliminating chipset dependency.
— If the target frequency is higher than the current frequency, V
in steps (+12.5 mV) by placing a new value on the VID signals and the
processor shifts to the new frequency. Note that the top frequency for the
processor can not be exceeded.
— If the target frequency is lower than the current frequency, the processor shifts
to the new frequency and V
changing the target VID through the VID signals.
7.4
System Management Bus (SMBus) Interface
The Intel
interface which allows access to a memory component with two sections (referred to as
the Processor Information ROM and the Scratch EEPROM). These devices and their
features are described below.
Note:
The SMBus on-package thermal sensor has been removed and is no longer used. Refer
to
Section 6.3
The processor SMBus implementation uses the clock and data signals of the System
Management Bus (SMBus) Specification. It does not implement the SMBSUS# signal.
For platforms which do not implement any of the SMBus features found on the
processor, all of the SMBus connections, except SM_VCC, to the socket pins may be left
unconnected (SM_CLK, SM_DAT, SM_EP_A[2:0], SM_WP).
116
Figure
®
Processor 7200 Series and 7300 Series have hardware logic that
®
®
Xeon
Processor 7200 Series and 7300 Series package includes an SMBus
for details about the new digital thermometer and PECI interface.
7-1. Enhanced Intel SpeedStep Technology
is then decremented in steps (-12.5 mV) by
CC
Features
is incremented
CC
Document Number: 318080-002
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