IBM System x3630 M3 Specification page 6

A cost-optimized storage-rich alternative to traditional enterprise 2U dual-socket servers
DDR3 Memory with Chipkill ECC Protection
The x3630 M3 ships with registered double data rate III (DDR3) memory and provides Active
Memory features, including advanced Chipkill memory protection standard or optionally (model-
specific), for up to 16X better error correction than standard ECC memory. In addition to offering
better performance than DDR2 or fully-buffered memory, DDR3 memory also uses less energy.
DDR2 memory already offered up to 37% lower energy use than fully buffered memory. Now, a
generation later, DDR3 memory is even more efficient, using up to 15% less energy than
registered DDR2 memory (and and even greater savings vs. fully buffered DDR2 memory).
The x3630 M3 currently supports up to 192GB of 1.5V RDIMM (registered DIMM) memory in 12
DIMM slots. The x3630 M3 also supports either standard 1.5V DIMMs or 1.35V DIMMs that
consume 19% less energy than 1.5V DIMMs. Redesign in the architecture of the Xeon 5500 and
5600 series processors bring radical changes in the way memory works in these servers. For
example, the Xeon 5500 and 5600 series processors integrate the memory controller inside
the processor, resulting in two memory controllers in a 2-socket system. Each memory controller
has three memory channels. Depending on the type of memory, population of memory, and
processor model, the memory may be clocked at 1333MHz, 1066MHz or 800MHz.
Notes: Adding a second processor not only doubles the amount of memory available for use, but
also doubles the number of memory controllers, thus doubling the system memory bandwidth. If
you add a second processor, but no additional memory for the second processor, the second
processor would have to access the memory from the first processor "remotely," resulting in
longer latencies and lower performance. The latency to access remote memory is almost 75%
higher than local memory access. So, the goal should be to always populate both processors with
memory.
The L5640 and X56xx processor models support up to 1333MHz memory clock speed. With new
single-rank and dual-rank RDIMMs, L5640 and X56xx processors support 2 DIMMs (running at
1.5V) per channel (2DPC) at 1333MHz. The E562x-and-up and L56xx models support a
maximum of 1066MHz clock speed (and thus memory access rate), and the E550x models
support 800MHz clock speed.
Running memory at 1333MHz (where supported) versus 1066MHz offers up to 9% better
performance, while memory running at 1066MHz produces up to 28% better performance than
memory running at 800MHz. Xeon 5500/5600 series processors access memory with almost
50% lower latency than the earlier 5400 series processors. That can result in faster processing
of latency-sensitive workloads.
Regardless of memory speed, the Xeon 5500/5600 platform represents a significant improvement
in memory bandwidth over the previous Xeon 5400 platform. At 1333MHz, the improvement is
almost 500% over the previous generation. This huge improvement is mainly due to the dual
integrated memory controllers and faster DDR3 1333MHz memory. Throughput at 800MHz is 25
gigabytes per second (GBps); at 1066MHz it's 32GBps; and at 1333MHz it's 35GBps. This
improvement translates into improved application performance and scalability.
Memory interleaving refers to how physical memory is interleaved across the physical DIMMs. A
balanced system provides the best interleaving. A Xeon 5500/5600 series processor-based
system is balanced when all memory channels on a socket have the same amount of memory.
The 5500 and 5600 series processors support single-, dual-, and quad-rank memory. A memory
rank is simply a segment of memory that is addressed by a specific address bit.
• A typical memory DIMM description is 4GB 2Rx4 DIMM
• The 2R designator is the rank count for this particular DIMM (2R = dual-rank)
• The x4 designator is the data width of the rank
It is important to ensure that DIMMs with the appropriate number of ranks are populated in each
channel for optimal performance. Whenever possible, use dual-rank DIMMs in the system. Dual-
6
Please see the Legal Information section for important notices and information.