Hemisphere Mode - HP ProLiant DL980 G7 Maintenance And Service Manual

system. Each buffer has two DDR3 channels and can support up to four DIMMs for a total of eight
DIMMs per cartridge.
Memory speed is not affected by number of DIMMs or ranks. All DIMMs run at the highest
possible speed for a given processor.
DDR3 memory speed is a function of the QPI bus speed supported by the processor:
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Processors with a QPI speed of 6.4 GT/s run memory at 1066 MT/s.
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Processors with a QPI speed of 5.6 GT/s run memory at 978 MT/s.
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Processors with a QPI speed of 4.8 GT/s run memory at 800 MT/s.
Successive cache lines are interleaved between the DIMMs and the Lockstep SMI channels of
the two memory controllers in the processor such that adjacent cache lines reside on different
memory controllers, SMIs, DIMMs, and DIMM ranks for better performance. To take advantage
of this feature, DIMMs should be populated evenly between all SMI channels. If an SMI channel
pair has more DIMMs than others, the extra memory on that SMI channel pair does not benefit
from the interleaving mechanism across memory controllers.

Hemisphere mode

The Intel® Xeon™ 7500-series processor architecture incorporates Hemisphere mode, a
high-performance interleaving technology. Hemisphere mode combines the tracking resources of
both memory controllers within each processor for a more aggressive cache line pipelining.
Hemisphere mode is the only supported configuration, and is enabled in RBSU when processors
in the system have identical DIMM population behind both of their memory controllers. That is to
say, all populated memory cartridges are populated the same way.
Hemisphere mode should produce the best overall performance for a variety of applications.
To enable each processor to enter Hemisphere mode, both memory cartridges must be installed
and populated with equal memory capacities based on the DIMM installation guidelines
("DIMM installation guidelines" (page
Greater performance is obtained when all cartridges are populated with either four or eight
dual- or quad-rank DIMMs.
The server supports Mirrored Memory mode while Hemisphere mode is enabled.
35)).
DIMMs 37