April 6, 2011

Intel Scales Up Cores and Memory with New Westmere EX CPUs

Michael Feldman

This week Intel launched its new Westmere EX lineup, the latest Xeons aimed at large-memory, multi-socketed servers. The new chips come in 6-, 8- and 10-core flavors and will be sold under the name Xeon E7. According to Intel, these latest CPUs deliver 40 percent greater performance than the previous generation Nehalem EX (Xeon 7500 and 6500) processors while maintaining the same power draw.

Compared to the 45nm-based Nehalem EX line, the E7 silicon is on 32nm process technology, which allowed them to add a couple of more cores and an additional 6 MB of L3 cache to the top-end chip. Despite that, Intel only grew the transistor count modestly, from 2.3 billion to 2.6 billion. The thrust was to make the cores smarter and more efficient at their job, not to rely on the brute force of Moore’s Law.

The E7s are 42 percent quicker than their Nehalem ancestors, at least at integer throughput (using the SPECint_rate_base2006 benchmark). One might wonder how Intel accomplished this since they only increased the core count and L3 cache by 25 percent apiece. Apparently 11 percent of the performance increase is the result of optimizations in the latest Intel Compiler XE2011. The rest of the performance bump can probably be attributed to the faster clock for the E7. (Intel pitted a 2.4 GHz E7-4870 against a 2.26 GHz Nehalem X7560 in their benchmark tests.) Floating point throughput (SPECfp_rate_base2006) increased at a more modest 32 percent.

Using the OpenMP benchmark (SPEC OMP2001) for shared memory throughput, the E7-4870 only delivered an 18 percent boost compared to the Nehalem X7560. On some real-life memory-intensive HPC workloads, however, performance was on par with the integer and FP results. For example, Intel reported that throughput improved 21 to 37 percent when exercising the E7s on a number of EDA analysis tools. It remains to be seen how other big memory HPC codes fare on the new hardware.

Besides the core count bump, the other notable E7 feature is its support for larger memory capacity. For a four-socket server, the E7 will scale up to 2 GB of RAM and 102 GB/second of bandwidth, which is twice as good as Nehalem EX. Intel accomplished this by adding support for 32 GB DIMM chips. (The E7 still relies on the same 16 DIMM slots per socket.) These 32 GB DIMMs tend to be rather expensive, though, and so far the server OEMs are only offering E7 systems with 16 GB DIMMs. But 1 TB in a four-socket box is quite useful in its own right, and will be able to handle some rather large in-memory databases.

Perhaps more importantly, the E7 chips can be paired with low voltage memory modules (LV DIMMs) to help curb energy consumption, especially on terascale-sized DRAM configurations. Intel has also added integrated memory buffers to further reduce power draw.

Unlike the Nehalem EX line, the E7 family is divided into three different processor series according chip socket support. The E7-2800 series is geared for two-socket systems, while the E7-4800 series is designed for machines with four CPUs. The quad-socket setup is probably the sweet spot for the E7 family given that four CPUs in one server is apt to be less expensive than 2 dual-socket boxes; plus you have twice the memory headroom. The E7-8800 series is for eight socket machines. These CPUs priced at a premium, but if you’re looking for an x86 SMP machine with up to 80 cores (160 threads) and multiple terabytes of memory, this is the CPU for you.

At launch, 19 server makers announced E7-based platforms, including the usual suspects like IBM, HP, Dell, Cisco, and Oracle. The principle destination for these chips will be “mission-critical” enterprise servers, the segment Intel first pursued in a major with its Nehalem EX line. To chase that application space, Intel has incorporated a number of new security and RAS features which, according to them, puts their latest x86 offering on par with RISC CPUs and even their own Itanium chip. Mission-critical enterprise computing is estimated to be worth about $18 billion per year — about twice that of the HPC server market.

But a number of vendors — SGI, Cray, Supermicro, and AMAX, thus far — are also using the E7s to build scaled-up HPC machinery. SGI for example, has latched onto the E7s to refresh their Altix UV shared memory products. The low-end Altix UV 10 and mid-range Altix UV 100 both benefitted from the extra cores and memory capacity.

For example, the UV 100 now scales to 960 cores and 12 TB of shared memory in just two racks. The top-of-the-line Altix UV 1000 can also use the new E7 CPUs, but for architectural reasons and OS limitations still tops out at 2,048 cores and 16 TB of memory. However, you can still take advantage of the more performant 8-core and 10-core E7s, so a UV 1000 can squeeze out more FLOPS per watt than before, and can scale past 20 teraflops of peak performance.

Cray’s CX1000-S is also being offered with E7 chips. Although, Cray didn’t announce specific configurations, as in the Altix UV, the higher performing E7s would make this SMP box faster and/or more power efficient.

Finally, both Supermicro and AMAX have come up with four-socket and eight-socket E7-based servers (these might actually be the same hardware). The top-end offerings delivers up to 80 cores and 2 TB of memory in an 5U form factor, while the four-socket servers provide half that scalability, but in a 1U, 2U, or 4U package. The 8-way offerings can be outfitted with up to four NVIDIA GPUs if you want to pair the E7 parts with some extra vector acceleration. Although these Supermicro and AMAX systems are geared for HPC, at least the non-GPU versions are also being positioned for big memory enterprise workloads.

As you can see from the chart above, these high-end CPUs are priced accordingly. The top-end 130-watt E7-8870 is over $4,600 in quantities of a thousand. More mid-range E7s will run half that, and even the 10-core chip for dual-socket systems runs over $2,500. Intel apparently believes that they are worth the premium, and given that these chip are being paired with lots of expensive DRAM and software, the CPU itself is probably the one of the best-valued components in these high-end shared memory servers.

Regardless, the E7 parts will be less expensive than RISC processors, the Itanium, or any proprietary CPU. At the other end of the price spectrum, Intel will have to contend with AMD, which is planning to launch its Bulldozer-class “Interlagos” CPU in Q3. Those chips come in 12-core and 16-core versions and can populate four-socket servers. So for users with SMP workloads that are chewing on terabytes of data, the x86 architecture is looking a bit more tempting.

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