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IBM Power 750 and 760 Technical Overview and Introduction
Processor core sleep mode
To be able to save even more energy, the processor has an even lower power
mode referred to as
sleep
. Before a core and its associated private L2 cache enter sleep
mode, the cache is flushed, transition lookaside buffers (TLB) are invalidated, and the
hardware clock is turned off in the core and in the cache. Voltage is reduced to minimize
leakage current. Processor cores inactive in the system (such as 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 chiplet enters the
winkle
mode. In this mode, the entire chiplet is turned off including the L3 cache. This
could 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
varies based on power consumption, ambient temperature, and altitude available. System
altitude can be set in IBM Director Active Energy Manager. If no altitude is set, the system
assumes a default value of 350 meters above sea level.
The Power 750 and the Power 760 comply to the ASHRAE Class A3 standard and can
support up to 35 degrees Celsius and 1825 meter at the rated performance. However, they
can operate in a degraded performance above 35 degrees Celsius up to 40 degrees
Celsius or higher altitudes.
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 longer in low-power idle
states (nap or sleep).
EnergyScale for I/O
IBM POWER7 and 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 POWER7 and 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 use, such as weekends. AEM
provides information, such as the power that will be saved and the time needed to bring a
server back online, that can be used to help make the decision to consolidate and power
off. As with many of the features that are available in IBM Systems Director and Active
Energy Manager, this function is scriptable and can be automated.