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higher output voltage from the IBC in
order to reduce the output current and
hence minimize distribution losses.
AVS is a technique used by leading
high-performance microprocessors to
optimize both the supply voltage and
clock frequency to ensure processing
demands are always satisfied with the
lowest possible power consumption.
AVS also enables automatic
compensation for the effects of silicon
process variations and changes in
operating temperature. To support
AVS, the PMBus specification has
recently been revised to define the
AVSBus, which allows a POL converter
to respond to AVS requests from an
attached processor.
Multicore activation on demand
provides a means of activating or
powering down individual cores of
a multicore processor in response
to changes in load. Clearly, de-
activating unused cores at times of
low processing load can help to gain
valuable energy savings.
Adaptive Techniques and
Potential Savings
These are the first adaptive features
to be implemented, as power
supply developers begin introducing
software-defined power architectures.
Many additional, powerful techniques
are expected to emerge, assisted by
the arrival in the market of PMBus-
fault management, sequencing, ramp-
up, and tracking.
As system designers are developing
more effective ways to exploit the
controllability PMBus brings, power
architectures are becoming software
defined and respond in real-time
to optimize efficiency. Some of
today’s most powerful techniques for
optimizing efficiency include Dynamic
Bus Voltage (DBV) optimization,
Adaptive Voltage Scaling (AVS), and
multicore activation on demand.
DBV provides a means of adjusting the
intermediate bus voltage dynamically
to suit prevailing load conditions. At
higher levels of server-power demand,
PMBus instructions can command a
Figure 2. PMBus-compatible converters allow digital optimization on the fly to optimize energy
efficiency.
30 l New-Tech Magazine Europe