IBM System x3400 M3 Product Manual page 6

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system. Dual-rank DIMMs offer better interleaving and hence better performance than single-rank
DIMMs. For instance, a system populated with six 2GB dual-rank DIMMs outperforms a system
populated with six 2GB single-rank DIMMs by 7% for SPECjbb2005. Dual-rank DIMMs are also
better than quad-rank DIMMs because quad-rank DIMMs will cause the memory speed to be
down-clocked.
Another important guideline is to populate equivalent ranks per channel. For instance, mixing one
single-rank DIMM and one dual-rank DIMM in a channel should be avoided.
Note: It is important to ensure that all three memory channels in each processor are populated. The
relative memory bandwidth decreases as the number of channels populated decreases. This is
because the bandwidth of all the memory channels is utilized to support the capability of the
processor. So, as the channels are decreased, the burden to support the requisite bandwidth is
increased on the remaining channels, causing them to become a bottleneck.
RDIMMs and UDIMMs cannot be used in the same server. Different brands of DIMMs should not be
mixed, due to possible timing issues.
For increased availability, the x3400 M3 offers an additional (but mutually exclusive) level of IBM
Active Memory protection: online memory mirroring.
Memory mirroring works much like disk mirroring. The total memory is divided into two channels.
Data is written concurrently to both channels. If a DIMM fails in one of the DIMMs in the primary
channel, it is instantly disabled and the mirrored (backup) memory in the other channel becomes
active (primary) until the failing DIMM is replaced. One-half of total memory is available for use with
mirroring enabled. (Note: Due to the double writes to memory, performance is affected.)
Mirroring is handled at the hardware level; no operating system support is required.
DDR3 memory is currently available in 1GB, 2GB, 4GB and 8GB RDIMMs, or 1GB, 2GB, and 4GB
UDIMMs. DIMMs are installed individually (not in pairs). However, for performance reasons, in a 2-
processor system, it's best to install matching DIMMs for each processor.
Maximum memory capacity and speed in 2-processor configurations include:
Memory Frequency
1333MHz (CTO only)
1333MHz (CTO only)
1066MHz
800MHz
800MHz-1333MHz
(Mirroring)
Hot-Swap/Redundant Components
System availability is maximized through the extensive use of hot-swap and redundant components,
including:
• Redundant memory protection (with memory mirroring enabled) and optional Chipkill
protection
• Hot-swap, redundant hard disk drives (with RAID protection standard)
• Hot-swap, redundant power supplies (model dependent)
High-Performance Adapter Slots
The x3400 M3 provides six adapter slots standard: five PCIe Gen 2 slots and one legacy PCI slot.
PCI Express Gen 2 is the next-generation of high-performance, low-latency, serial I/O bus. Slot 2 is
a x16 ("by 16") physical/x8 electrical PCIe (PCI Express) Gen 2 slot. This means that although the
slot runs at x8 Gen 2 speeds (8GBps), it can accept a x16 Gen 2 adapter in the slot. It is also
capable of supporting x1/x4/x8 adapters at full speed. In addition to this slot, the x3400 M3 also
includes two x8 physical/x8 electrical Gen 2 slots (8GBps), two x8 physical/x4 electrical Gen 2
slots (4GBps), and one 33MHz legacy PCI slot. As part of a configure-to-order (CTO) build, two
choices of riser card can be added, with either two 133MHz PCI-X slots (8 total) or one PCIe x8
physical/x4 electrical Gen 1 (2GBps) slot (7 total).
Slot 1 is a half-length/full-height PCIe slot; slots 2, 3, 4 and 5 are full-length/full-height PCIe
DIMMs per Max. Memory
Channel Capacity
1 48GB RDIMM
(6 DIMMs) 24GB UDIMM
2 96GB RDIMM
(12 DIMMs) 48GB UDIMM
2 96GB RDIMM
(12 DIMMs) 48GB UDIMM
3 128GB RDIMM
(16 DIMMs) 48GB UDIMM
3 96GB RDIMM
(12 DIMMs) 24GB UDIMM
Processors
X5650 and above
X5650 and above
E5603 and above
E5603, and above
E5603, L5609, and above
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