IBM Power 720 Overview page 69

Figure 2-9 shows memory location codes and how the memory riser cards are divided in
quads, each quad being attached to a memory buffer.
Quad A
Quad B
Figure 2-9 Memory Riser Card for Power 720 and Power 740 Systems
The memory-placement rules are as follows:
The base machine contains one memory riser card with eight DIMM sockets. Memory
features occupy two memory DIMM sockets.
One additional memory riser card feature (1 x FC EM01, CCIN 2C1C) with an additional
eight DIMM sockets is available when one processor module is installed in the system. For
the Power 740, three optional memory riser card features (3 x FC EM01, CCIN 2C1C) with
an additional eight DIMM sockets per feature are available when two processor modules
are installed in the system.
Each DIMM within a DIMM quad must be equivalent. However, Quad B DIMMs can be
different from the Quad A DIMMs. A quad does not have to be filled before putting another
pair of DIMMs into another quad.
Mixing features FC EM08, FC EM4B, FC EM4C, or FC EM4D is supported on the same
memory riser card while there is only one type of memory DIMM in the same quad.
Generally, the best way is to install memory evenly across all memory riser cards in the
system. Balancing memory across the installed memory riser cards allows memory access in
a consistent manner and typically results in the best possible performance for your
configuration. However, balancing memory fairly evenly across multiple memory riser cards,
compared to balancing memory exactly evenly, typically has a small performance difference.
Be sure to account for any plans for future memory upgrades when you are deciding which
memory feature size to use at the time of initial system order.
Buffer B
Memory Riser Card
Chapter 2. Architecture and technical overview
Slot #1 – P1-Cn-C1
Slot #2 – P1-Cn-C2
Slot #3 – P1-Cn-C3
Slot #4 – P1-Cn-C4
Buffer A
Slot #5 – P1-Cn-C7
Slot #6 – P1-Cn-C8
Slot #7 – P1-Cn-C9
Slot #8 – P1-Cn-C10
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