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AMDEPYCInfinityFabricv.IntelBroadwell-EPQPIArchitectureExplained–E-ENERGYHOLDINGLIMITED

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AMD EPYC Infinity Fabric V Intel Broadwell DE QPI

Ever since the AMD EPYC launched we have gotten a barrage of questions on the architecture. Many of these questions come in the form of “so and so YouTube vlogger/ gaming website said EPYC is all one chip and STH is wrong,” or “AMD EPYC is always better than Intel’s architecture,” and conversely “Intel Xeon E5-2600 V4’s will always smoke AMD EPYC.” All of those statements are patently false. There are four NUMA nodes and pieces of silicon on each EPYC package. They are tied together with Infinity Fabric. This makes total sense based on what we have seen in the lab. 46w0712

To help our readers understanding the new AMD EPYC Infinity Fabric architecture versus the Broadwell-EP generation, and by extension, the rest of the Intel Xeon E5-2600 V1-V4 generations, we put together a quick video showing differences in design philosophies.

Some Background on Where and Why

STH was perhaps the first 3rd party independent site to have AMD EPYC hardware in the data center. At STH, we keep dozens of Intel Xeon CPUs online in the data center just to be able to run performance regressions with new benchmarks on older chips for clients. While we are still awaiting some of our performance data to settle (e.g. with new firmware that came in over the past few days) we feel confident saying AMD has some great use cases. At the same time, there are plenty of use cases where the Intel Xeon E5-2600 V4 generation performs well.

In Q3 2017 we will, for the first time in 5+ years, have competition in the server market again. Accordingly, there are now more considerations to purchasing decisions than simply buying the next generation of Intel Xeon E5-2620 V3 to E5-2620 V4 or buying more cores/ higher clocks. For the first time in years, we have a legitimate, competitive x86 architecture. As an IT and technology industry, those purchasing new gear do need to add another domain of knowledge to address these new developments.

At launch, AMD provided this slide showing dual socket Infinity Fabric. We wanted to add a bit more information beyond what this view shows and also help our readers compare to Intel.

Although this is a great graphic, AMD is actually doing a lot more with Infinity Fabric than one may see at first glance.

AMD EPYC Infinity Fabric v. Intel Broadwell-EP QPI and NUMA Nodes

To understand why the AMD Infinity Fabric design both makes sense for AMD’s business model and why Intel Broadwell-EP is different here is the video we made:

Although at STH we are primarily creating content that is easy to read without speakers and in planes (I am typing this from the Lufthansa Lounge en route to San Francisco from Munich), this discussion requires a video.

In the video we show why the eight NUMA nodes in a dual socket AMD EPYC Infinity Fabric is a complex engineering marvel. We also show why a dual socket AMD EPYC platform is going to rely on the Infinity Fabric to a much higher degree than Intel’s QPI will be used in a dual socket system.

After watching, you should understand why comparing QPI speed and bandwidth v. Infinity Fabric speed and bandwidth is not an apples-to-apples comparison. In the Intel design, ~50% of resources can sit on the other side of the link while with AMD ~87.5% of system resources will be across one or two Infinity Fabric hops.

Final Words

With Skylake-SP launching, we will have an update comparing the next-gen Intel architecture to what AMD has as there are some differences. Expect more data in our upcoming pieces for the new Intel Xeon Platinum, Gold, Silver and Bronze family. We are also working on characterizing the performance of AMD EPYC v. Intel Xeon E5 and Platinum, Gold, Silver, and Bronze to help our readers understand which is better. As the different firmware and kernel versions change, we are seeing some drastic swings in performance. Once the dust settles, we will have more.

For those wondering, we do not see AMD EPYC competing against Intel Broadwell-EP (Xeon E5-2600 V4.) General availability of systems from major vendors such as Dell EMC, HPE, and Supermciro, along with others, will likely be in mid-Q3 2017. While AMD “launched” first, in the market AMD will be shipping alongside Intel Skylake-SP. We still wanted to post this video for those who need to explain how current systems compare to AMD EPYC Infinity Fabric.

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