106 IBM Power 750 and 760 Technical Overview and Introduction
Power saver mode is not supported during boot or reboot, although it is a persistent
condition that will be sustained after the boot when the system starts executing
instructions.
Dynamic power saver mode
Dynamic power saver mode varies processor frequency and voltage based on the
utilization of the POWER7 or POWER7+ processors. Processor frequency and utilization
are inversely proportional for most workloads, implying that as the frequency of a
processor increases, its utilization decreases, given a constant workload. Dynamic power
saver mode takes advantage of this relationship to detect opportunities to save power,
based on measured real-time system utilization.
When a system is idle, the system firmware lowers the frequency and voltage to power
energy saver mode values. When fully utilized, the maximum frequency varies, depending
on whether the user favors power savings or system performance. If an administrator
prefers energy savings and a system is fully utilized, the system is designed to reduce the
maximum frequency to about 95% of nominal values. If performance is favored over
energy consumption, the maximum frequency can be increased to up to 112.8% of
nominal frequency for extra performance.
The maximum frequency is reached by using the dynamic power saver mode when the
system approaches full utilization. To get a high processor frequency independent from
the utilization of the system, a processor feature code with a higher clock speed should be
ordered.
Table 2-30 shows the maximum frequency increases of the various processor options.
Table 2-30 Maximum frequency increase values for Power 750 and Power 760
Dynamic power saver mode is mutually exclusive with power saver mode. Only one of
these modes can be enabled at a given time.
Processor module option Power 750 Power 760
3.5 GHz 8-core DCM 12.8%
4.0 GHz 8-core DCM 9.0%
3.1 GHz 12-core DCM 10.7%
3.4 GHz 12-core DCM 10.7%
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