IBM BladeCenter HS23, Product Manual, Page: 11 / 28

IBM BladeCenter HS23 11
Memory options
IBM DDR3 memory is compatibility tested and tuned for optimal IBM System x® and BladeCenter
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 BladeCenter HS23 supports Very Low Profile (VLP) DDR3 memory RDIMMs. The server supports up
to eight DIMMs when one processor is installed and up to 16 DIMMs when two processors are installed.
Each processor has four memory channels, and there are two DIMMs per channel. The following rules
apply when selecting the memory configuration:
Mixing 1.5 V and 1.35 V DIMMs in the same server is supported. In such a case all DIMMs operate at

1.5 V.
The maximum number of ranks supported per channel is eight.

The maximum quantity of DIMMs that can be installed in the server depends on the number of CPUs,

DIMM rank, and operating voltage, as shown in the "Max. qty supported" row in Table 7.
All DIMMs in all CPU memory channels operate at the same speed, which is determined as the

lowest value of:
Memory speed supported by specific CPU

Lowest maximum operating speed for the selected memory configuration that depends on rated

speed, as shown under the "Max. operating speed" section in Table 7.
Table 7. Maximum memory speeds
DIMM type
DIMM specification
RDIMM
Rank Single rank Dual rank
Rated speed 1333 MHz 1600 MHz 1333 MHz 1600 MHz
Rated voltage 1.35 V 1.5 V 1.35 V 1.5 V
Operating voltage 1.35 V 1.5 V 1.5 V 1.35 V 1.5 V 1.5 V
Max. qty supported* 16 16 16 16 16 16
Max. DIMM capacity 4 GB 4 GB 4 GB 16 GB 16 GB 8 GB
Max. memory capacity 64 GB 64 GB 64 GB 256 GB 256 GB 128 GB
Max. operating speed (MHz) ______ ______ ______ _______ _______ _______
1 DIMM per channel 1333 1333 1600 1333 1333 1600
2 DIMMs per channel 1333 1333 1600 1333 1333 1600
* The maximum quantity supported is shown for two processors installed. When one processor is installed the
maximum quantity supported is a half of that shown.
The following memory protection technologies are supported:
ECC

Memory mirroring

Memory sparing (rank sparing)

If memory mirroring is used, then DIMMs must be installed in pairs (minimum of one pair per CPU), and
both DIMMs in a pair must be identical in type and size. The effective memory available to the system is
only half of that installed.