IBM System x3550 M4
10
Memory options
IBM DDR3 memory is compatibility tested and tuned for optimal IBM System x® performance and
throughput. IBM memory specifications are integrated into the light path diagnostics for immediate system
performance feedback and optimum system uptime. From a service and support standpoint, IBM memory
automatically assumes the IBM system warranty, and IBM provides service and support worldwide.
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.
z
Mixing 1.5 V and 1.35 V DIMMs in the same server is supported; in such cases, all DIMMs operate at
z
1.5 V.
The maximum number of ranks supported per one channel is eight (with the exception of Load
z
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
z
type, rank, and operating voltage as shown in the "Max. quantity" row in Table 4.
All DIMMs in all CPU memory channels operate at the same speed, which is determined as the
z
lowest value of:
The memory speed supported by the specific CPU.
z
The lowest of maximum operating speeds for the selected memory configuration that depends on
z
rated speed, operating voltage, and quantity of DIMMs per channel, as shown under "Maximum
operating speed" section in Table 4.
Table 4. Maximum memory speeds
Specification
UDIMMs
RDIMMs
LRDIMMs
Rank
Dual rank
Single rank
Dual rank
Quad rank
Quad rank
Rated speed
1333 MHz
1333 MHz
1600
MHz
1333 MHz
1600
MHz
1066 MHz
1333 MHz
Rated voltage
1.35 V
1.35 V
1.5 V
1.35 V
1.5 V
1.35 V
1.35 V
Operating
voltage
1.35 V
1.5 V
1.35 V
1.5 V
1.5 V
1.35 V
1.5 V
1.5 V
1.35 V
1.5 V
1.35 V
1.5 V
Max quantity*
16
16
16
24
24
16
24
24
16
16
24
24
Largest DIMM
4 GB
4 GB
4 GB
4 GB
4 GB
16 GB
16 GB
8 GB
8 GB
8 GB
32 GB
32 GB
Max memory
capacity
64 GB
64 GB 64 GB
96 GB 96 GB 256 GB 384 GB 192 GB 128 GB 128 GB 768 GB 768 GB
Max memory
at max speed
32 GB
64 GB 64 GB
64 GB 64 GB 256 GB 256 GB 128 GB 128 GB 64 GB
256 GB 512 GB
Maximum operating speed (MHz)
1 DIMMs
per channel
1333
MHz
1333
MHz
1333
MHz
1333
MHz
1600
MHz
1333
MHz
1333
MHz
1600
MHz
800
MHz
1066
MHz
1333
MHz
1333
MHz
2 DIMMs
per channel
1066
MHz
1333
MHz
1333
MHz
1333
MHz
1600
MHz
1333
MHz
1333
MHz
1600
MHz
800
MHz
800
MHz
1066
MHz
1333
MHz
3 DIMMs
per channel
NS**
NS**
NS**
1066
MHz
1066
MHz
NS**
1066
MHz
1066
MHz
NS**
NS**
1066
MHz
1066
MHz
* 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
