Product guide

Ultrascalability in a 2-socket package, combined with extreme availability features and industry-
leading performance
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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.
For peak performance:
• Populate both processors with equal amounts of memory to enable a balanced NUMA
system.
• Populate both memory controllers within a processor with equal memory capacity.
• Populate an even number of ranks per channel.
• Use dual-rank DIMMs whenever appropriate.
Power guidelines:
• Fewer larger DIMMs (for example 8 x 4GB DIMMs vs. 16 x 2GB DIMMs will generally have
lower power requirements
• x8 DIMMs (x8 data width of rank) will generally draw less power than equivalently sized x4
DIMMs
Reliability guidelines:
• Using fewer, larger DIMMs (for example 8 x 4 GB DIMMs vs. 16 x 2GB DIMMs is generally
more reliable
• Memory controllers support IBM Chipkill memory protection technology with x4 DIMMs (x4
data width of rank) and x8 DIMMs
For increased availability beyond Chipkill error correction, the eX5 servers offer additional levels
of IBM Active Memory protection:
Memory ProteXion technology provides multichip error protection and works in conjunction with
Chipkill technology—which provides multibit protection per chip—and standard ECC protection,
to provide multi-level memory correction.
Memory scrubbing is an automatic daily test of all system memory. It detects and reports
memory errors that might be developing before they cause a server outage. Memory scrubbing
and Memory ProteXion work together. When a bit error is detected, memory scrubbing
determines whether the error is recoverable. If the error is recoverable Memory ProteXion
technology will write the data to new location; if it is not recoverable, scrubbing sends an alert to
light path diagnostics, which then notifies IBM Systems Director.
Memory mirroring works much like disk mirroring. The total memory is divided into two
channels, a primary and a backup. Data is written concurrently to both channels. If one of the
DIMMs in the primary channel fails, it is instantly disabled and the mirrored memory in the
backup channel becomes active (primary) until the failing DIMM is replaced. With mirroring
enabled, one-half of total memory is available for use.
Alternatively, with memory rank sparing, two ranks per memory card are configured as spares.
These spare ranks are used in the event of a memory failure on the same memory card. This
feature is more efficient than mirroring, reserving less memory and leaving more available for
operating system use. (A memory card using dual-rank DIMMs, for example, would have up to
16 ranks, 14 available.)
Memory is available in 1GB, 2GB, 4GB, 8GB, 16GB or 32GB DIMMs
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High-Performance Scalability
Memory scalability beyond the 1TB capacity of the x3690 X5 chassis is achieved simply by
cabling a 1U MAX5 memory expansion unit to the chassis. It doubles memory capacity by
adding another 32 DIMMs slots for up to 1TB of additional memory (2TB total in only 3U of rack
space).
The MAX5 scalability and memory expansion feature is a unique IBM enhancement, not offered
by other x86 server architectures.
High-Performance Adapter Slots
There are five PCIe (PCI Express) Gen 2 adapter slots standard. PCI Express Gen 2 is the
latest high-performance, low-latency, next-generation serial I/O bus. Slot 1 is a 3/4-length/full-
height slot. Slot 2 is half-length/full-height. Slots 3 through 5 are low-profile. Slots 1, 2, 3 and
5 are x8 (“by 8”) slots, both physically and electrically (meaning they operate at the full x8
8GBps
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bidirectional speed). Slot 4 is physically x8 but electrically x4, which means it can
accept a x8 adapter, but it will operate at x4 speeds (4GBps). If a ServeRAID controller is
installed, it will go in Slot 4. If a 10Gb Ethernet Adapter is installed, it will go in Slot 5. If you
require a x16 adapter slot, an optional riser card containing one full-length/full-height x16/x16
slot can be added as a replacement for the riser card containing Slots 1 and 2.