IBM Redboks System x3550 M4, User Manual

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IBM System x3550 M4 12
The IBM System x3550 M4 supports DDR3 memory. The server supports up to 12 DIMMs when one
processor is installed, and up to 24 DIMMs when two processors are installed. Each processor has four
memory channels, and there are three DIMMs per channel.
The following rules apply when selecting the memory configuration:
Mixing different types of memory (UDIMMs, RDIMMs, and LRDIMMs) is not supported.

Mixing 1.5 V and 1.35 V DIMMs in the same server is supported; in such cases, all DIMMs operate at

1.5 V.
The maximum number of ranks supported per one channel is eight (with the exception of Load

Reduced DIMMs, where more than eight ranks are supported because one quad-rank LRDIMM
provides the same electrical load on a memory bus as a single-rank RDIMM).
The maximum quantity of DIMMs that can be installed in server depends on number of CPUs, DIMM

type, rank, and operating voltage as shown in the "Maximum quantity" row in the following table.
All DIMMs in all CPU memory channels operate at the same speed, which is determined as the

lowest value of:
The memory speed supported by the specific CPU.

The lowest of maximum operating speeds for the selected memory configuration that depends on

rated speed, operating voltage, and quantity of DIMMs per channel, as shown under "Maximum
operating speed" section in the following table.
The following table (Parts 1 and 2) shows the characteristics of the supported DIMMs. Tables cells
highlighted with a gray background indicate when the combination of DIMM voltage and the number of
DIMMs per channel still allows the DIMMs to operate at a rated speed.
Table 5. Maximum memory speeds (Part 1: RDIMMs)
Specification RDIMMs
Rank Single rank Dual rank Quad rank
Part numbers 49Y1405 (2 GB)
49Y1406 (4 GB) 49Y1559 (4 GB) 49Y1407 (4 GB)
49Y1397 (8 GB)
49Y1563 (16 GB)
90Y3178 (4 GB)
90Y3109 (8 GB)
00D4968 (16 GB)
49Y1399 (8 GB)
Rated speed 1333 MHz 1600 MHz 1333 MHz 1600 MHz 1066 MHz
Rated voltage 1.35 V 1.5 V 1.35 V 1.5 V 1.35 V
Operating voltage 1.35 V 1.5 V 1.5 V 1.35 V 1.5 V 1.5 V 1.35 V 1.5 V
Maximum quantity* 16 24 24 16 24 24 16 16
Largest DIMM 4 GB 4 GB 4 GB 16 GB 16 GB 16 GB 8 GB 8 GB
Maximum memory
capacity 64 GB 96 GB 96 GB 256 GB 384 GB 384 GB 128 GB 128 GB
Maximum memory
at rated speed 64 GB 64 GB 64 GB 256 GB 256 GB 256 GB 128 GB 64 GB
Maximum operating speed (MHz)
1 DIMM per channel 1333 MHz 1333 MHz 1600 MHz 1333 MHz 1333 MHz 1600 MHz 800 MHz 1066 MHz
2 DIMMs per channel 1333 MHz 1333 MHz 1600 MHz 1333 MHz 1333 MHz 1600 MHz 800 MHz 800 MHz
3 DIMMs per channel NS** 1066 MHz 1066 MHz NS** 1066 MHz 1066 MHz NS** NS**
* Maximum quantity supported is shown for two processors installed. When one processor installed the maximum
quantity supported is a half of shown.
** NS = Not Supported