Harness High Performance with the X3950 M2 Model

Combining high-performance architecture with high-performance Xeon processors

I II I

MT/s

2.5GT/s IB: 2 x12

SP: 3 x8

eX4 chipset

South ES

Bridge

I/F LP

Flash

I/F

				2.1
N	N	N	N	s

Memory

DIMMS

533

Scalable Virtual L4

MT/s

cache

twice as many FSBs as before and each is 60% faster than before.

Intel Extended Memory 64 Technology (EM64T) 64-bit extensions allow the Xeon processor to use large memory addressing when running with a 64-bit operating system. This in turn lets individual software processes directly access more than 4GB of RAM, which was the limit of 32- bit addressing. This can result in much higher performance for certain kinds of programs, such as database management and CAD. Additional registers and instructions (SSE3) can further boost performance for applications written to use them. Customers should contact their software provider to determine their software support for EM64T.

Intel’s Virtualization Technology (VT) integrates hardware-level virtualization hooks that allow operating system vendors to better utilize the hardware for virtualization workloads, a key workload for the eX4 platform.

eX4 Chipset ‘Snoop’ Filtering

One of the core features of the eX4 chipset that gives the platform a performance advantage is the snoop filter. The Xeon Coherency Protocol or “snoop” is an operation that occurs whenever a processor in an SMP system needs to update a memory address during normal operation.

The snoop occurs when the processor getting ready to operate on a piece of data asks the other processors in the SMP complex to verify they have not modified the same piece of data without writing back from their cache. This operation increases traffic on the front side bus.

The eX4 chipset contains 324MB of EDRAM within the Northbridge chip. This copies all data as it is written to the processor cache, allowing the chipset to respond directly to the snoop requests. This reduces the overall traffic across the FSB and helps to improve system performance over other architectures. (Intel now offers a first-generation snoop filter in their

7300 chipset; however it contains only 64MB of RAM which is 80% smaller than the eX4 fourth- generation solution.)

Advanced Buffer eXecution

The IBM Advanced Buffer eXecution (ABX) chips (2 per chassis) provide the x3850 M2 /

3950 M2’s DDR2 memory with up to 60% more bandwidth than other vendors can manage using more expensive (and more

energy-hungry) Fully Buffered DIMMs (FB-DIMMs). The ABX chip uses two buffers per

memory card to re-drive the signals from the eX4 memory controller to the DIMMs,

bypassing the latency-adding buffers used on each FB-DIMM. The use of ABX reduces

latency by 20% vs. FB-DIMMs.

This feature is a unique IBM enhancement, not offered by other x86 server architectures (using either Intel or AMD processors).

XceL4v Dynamic Server Cache

Another performance feature of the eX4 chipset is the XceL4v L4 cache. When using a single node (chassis), the cache works with the snoop filter to help reduce FSB traffic. When more than one node is used, 256MB of virtual cache per node (taken from main memory) is used for interprocessor communications between chassis, to keep data in synch. In a 4chassis configuration, this amounts to as much as 1GB of L4 cache. This not only compensates for any performance hit that might otherwise result from sending data across the distances between processors in multiple chassis, it actually results in a performance improvement versus a single chassis. (IBM X3 and eX4 servers have achieved well over 100 #1 results on industry-standard benchmarks, such as TPC-C, TPC-E, TPC-H, SAP SD, vConsolidate, Vmark, and more.)

This feature is a unique IBM enhancement, not offered by other x86 server architectures (using either Intel or AMD processors).

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