Specifications

Chapter 4. Product information and technology 113
򐂰 Soft power capping
Soft power capping extends the allowed energy capping range further,
beyond a region that can be guaranteed in all configurations and conditions.
When an energy management goal is to meet a particular consumption limit,
soft power capping is the mechanism to use.
򐂰 Processor core nap
The IBM POWER7 processor uses a low-power mode called
nap that stops
processor execution when there is no work to be done by that processor core.
The latency of exiting nap falls within a partition dispatch (context switch),
such that the IBM POWER Hypervisor™ uses it as a general purpose idle
state. When the operating system detects that a processor thread is idle, it
yields control of a hardware thread to the POWER Hypervisor. The POWER
Hypervisor immediately puts the thread into nap mode. Nap mode allows the
hardware to clock-off most of the circuits inside the processor core. Reducing
active energy consumption by turning off the clocks allows the temperature to
fall, which further reduces leakage (static) power of the circuits, causing a
cumulative effect. Unlicensed cores are kept in core nap mode until they are
licensed, and they return to core nap mode when unlicensed again.
򐂰 Processor folding
Processor folding is a consolidation technique that dynamically adjusts, over
the short term, the number of processors available for dispatch to match the
number of processors demanded by the workload. As the workload
increases, the number of processors made available increases. As the
workload decreases, the number of processors made available decreases.
Processor folding increases energy savings during periods of low to moderate
workload, because unavailable processors remain in low-power idle
states longer.
򐂰 EnergyScale for I/O
IBM POWER processor-based systems automatically power off pluggable,
Peripheral Component Interconnect (PCI) adapter slots that are empty or not
being used. System firmware automatically scans all pluggable PCI slots at
regular intervals, looking for the ones that meet the criteria of not being in use
and powering them off. This support is available for all POWER
processor-based servers and the expansion units they support.
4.12.2 EnergyScale device
The EnergyScale device dynamically optimizes processor performance,
depending on the processor power and system workload.