Specifications

5102ch02.fm Draft Document for Review May 12, 2014 12:46 pm
72 IBM Power System S822 Technical Overview and Introduction
leakage current. Processor cores that are inactive in the system (such as capacity on
demand, CoD, processor cores) are kept in sleep mode. Sleep mode saves about 80%
power consumption in the processor core and its associated private L2 cache.
򐂰 Processor chip winkle mode
The most amount of energy can be saved when a whole POWER8 chiplet enters the
winkle mode. In this mode the entire chiplet is turned off including the L3 cache. This way
can save more than 95% power consumption.
򐂰 Fan control and altitude input
System firmware dynamically adjusts fan speed based on energy consumption, altitude,
ambient temperature, and energy savings modes. Power Systems are designed to
operate in worst-case environments, in hot ambient temperatures, at high altitudes, and
with high-power components. In a typical case, one or more of these constraints are not
valid. When no power savings setting is enabled, fan speed is based on ambient
temperature and assumes a high-altitude environment. When a power savings setting is
enforced (either Power Energy Saver Mode or Dynamic Power Saver Mode), fan speed
will vary based on power consumption and ambient temperature.
򐂰 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 that are made
available decreases. Processor folding increases energy savings during periods of low to
moderate workload because unavailable processors remain in low-power idle states (nap
or sleep) longer.
򐂰 EnergyScale for I/O
IBM POWER8 processor-based systems automatically power off hot pluggable PCI
adapter slots that are empty or not being used. System firmware automatically scans all
pluggable PCI slots at regular intervals, looking for those that meet the criteria for being
not in use and powering them off. This support is available for all POWER8
processor-based servers and the expansion units that they support.
򐂰 Server power down
If overall data center processor utilization is low, workloads can be consolidated on fewer
numbers of servers so that some servers can be turned off completely. Consolidation
makes sense when there will be long periods of low utilization, such as weekends. Live
Partition Mobility can be used to move workloads to consolidate partitions onto fewer
systems, reducing the number of servers powered on and therefore reducing the power
usage.