Sizing Up Servers: Intel's Skylake-SP Xeon versus AMD's EPYC 7000 - The Server CPU Battle of the Decade?
by Johan De Gelas & Ian Cutress on July 11, 2017 12:15 PM EST- Posted in
- CPUs
- AMD
- Intel
- Xeon
- Enterprise
- Skylake
- Zen
- Naples
- Skylake-SP
- EPYC
Single Threaded Integer Performance: SPEC CPU2006
Even in the server market where high core count CPUs are ruling the roost, high single threaded performance is still very desirable. It makes sure that a certain level of performance is guaranteed in every situation, not just in "throughput situations" of "embarrassingly parallel" software.
SPEC CPU2017 has finally launched, but it did so while our testing was already under way. So SPEC CPU2006 was still our best option to evaluate single threaded performance. Even though SPEC CPU2006 is more HPC and workstation oriented, it contains a good variety of integer workloads.
It is our conviction that we should try to mimic how performance critical software is compiled instead of trying to achieve the highest scores. To that end, we:
- use 64 bit gcc : by far the most used compiler on linux for integer workloads, good all round compiler that does not try to "break" benchmarks (libquantum...) or favor a certain architecture
- use gcc version 5.4: standard compiler with Ubuntu 16.04 LTS. (Note that this is upgraded from 4.8.4 used in earlier articles)
- use -Ofast -fno-strict-aliasing optimization: a good balance between performance and keeping things simple
- added "-std=gnu89" to the portability settings to resolve the issue that some tests will not compile with gcc 5.x
- run one copy of the test
The ultimate objective is to measure performance in non-"aggressively optimized" applications where for some reason – as is frequently the case – a "multi-thread unfriendly" task keeps us waiting.
First the single threaded results. It is important to note that thanks to modern turbo technology, all CPUs will run at higher clock speeds than their base clock speed.
- The Xeon E5-2690 ("Sandy Bridge") is capable of boosting up to 3.8 GHz
- The Xeon E5-2690 v3 ("Haswell") is capable of boosting up to 3.5GHz
- The Xeon E5-2699 v4 ("Broadwell") is capable of boosting up to 3.6 GHz
- The Xeon 8176 ("Skylake-SP") is capable of boosting up to 3.8 GHz
- The EPYC 7601 ("Naples") is capable of boosting up to 3.2 GHz
First we look at the absolute numbers.
| Subtest | Application type | Xeon E5-2690 @ 3.8 |
Xeon E5-2690 v3 @ 3.5 |
Xeon E5-2699 v4 @ 3.6 |
EPYC 7601 @3.2 |
Xeon 8176 @3.8 |
| 400.perlbench | Spam filter | 35 | 41.6 | 43.4 | 31.1 | 50.1 |
| 401.bzip2 | Compression | 24.5 | 24.0 | 23.9 | 24.0 | 27.1 |
| 403.gcc | Compiling | 33.8 | 35.5 | 23.7 | 35.1 | 24.5 |
| 429.mcf | Vehicle scheduling | 43.5 | 42.1 | 44.6 | 40.1 | 43.3 |
| 445.gobmk | Game AI | 27.9 | 27.8 | 28.7 | 24.3 | 31.0 |
| 456.hmmer | Protein seq. analyses | 26.5 | 28.0 | 32.3 | 27.9 | 35.4 |
| 458.sjeng | Chess | 28.9 | 31.0 | 33.0 | 23.8 | 33.6 |
| 462.libquantum | Quantum sim | 55.5 | 65.0 | 97.3 | 69.2 | 102 |
| 464.h264ref | Video encoding | 50.7 | 53.7 | 58.0 | 50.3 | 67.0 |
| 471.omnetpp | Network sim | 23.3 | 31.3 | 44.5 | 23.0 | 40.8 |
| 473.astar | Pathfinding | 25.3 | 25.1 | 26.1 | 19.5 | 27.4 |
| 483.xalancbmk | XML processing | 41.8 | 46.1 | 64.9 | 35.4 | 67.3 |
As raw SPEC scores can be a bit much to deal with in a dense table, we've also broken out our scores on a percentage basis. Sandy Bridge EP (Xeon E5 v1) is about 5 years old, the servers based upon this CPU are going to get replaced by newer ones. So we've made "Single threaded Sandy Bridge-EP performance" our reference (100%) , and compare the single threaded performance of all other architectures accordingly.
| Subtest | Application type | Xeon E5-2690 @ 3.8 |
Xeon E5-2690 v3 @ 3.5 |
Xeon E5-2699 v4 @ 3.6 | EPYC 7601 @3.2 | Xeon 8176 @ 3.8 |
| 400.perlbench | Spam filter | 100% | 119% | 124% | 89% | 143% |
| 401.bzip2 | Compression | 100% | 98% | 98% | 98% | 111% |
| 403.gcc | Compiling | 100% | 105% | 70% | 104% | 72% |
| 429.mcf | Vehicle scheduling | 100% | 97% | 103% | 92% | 100% |
| 445.gobmk | Game AI | 100% | 100% | 103% | 87% | 111% |
| 456.hmmer | Protein seq. analyses | 100% | 106% | 122% | 105% | 134% |
| 458.sjeng | Chess | 100% | 107% | 114% | 82% | 116% |
| 462.libquantum | Quantum sim | 100% | 117% | 175% | 125% | 184% |
| 464.h264ref | Video encoding | 100% | 106% | 114% | 99% | 132% |
| 471.omnetpp | Network sim | 100% | 134% | 191% | 99% | 175% |
| 473.astar | Pathfinding | 100% | 99% | 103% | 77% | 108% |
| 483.xalancbmk | XML processing | 100% | 110% | 155% | 85% | 161% |
SPEC CPU2006 analysis is complicated, and with only a few days spend on the EPYC server, we must admit that what follows is mostly educated guessing.
First off, let's gauge the IPC efficiency of the different architectures. Considering that the EPYC core runs at 12-16% lower clockspeeds (3.2 vs 3.6/3.8 GHz), getting 90+% of the performance of the Intel architectures can be considered a "strong" (IPC) showing for the AMD "Zen" architecture.
As for Intel's latest CPU, pay attention to the effect of the much larger L2-cache of the Skylake-SP core (Xeon 8176) compared to the previous generation "Broadwell". Especially perlbench, gobmk, hmmer and h264ref (the instruction part) benefit.
Meanwhile with the new GCC 5.4 compiler, Intel's performance on the "403.gcc benchmark" seems to have regressed their newer rchitectures. While we previously saw the Xeon E5-2699v4 perform at 83-95% of the "Sandy Bridge" Xeon E5-2690, this has further regressed to 70%. The AMD Zen core, on the other hand, does exceptionally well when running GCC. The mix of a high percentage of (easy to predict) branches in the instruction mix, a relatively small footprint, and a heavy reliance on low latency (mostly L1/L2/8 MB L3) seems to work well. The workloads where the impact of branch prediction is higher (somewhat higher percentage of branch misses) - gobmk, sjeng, hmmer - perform quite well on "Zen" too, which has a much lower branch misprediction penalty than AMD's previous generation architecture thanks to the µop cache.
Otherwise the pointer chasing benchmarks – XML procesing and Path finding – which need a large L3-cache, are the worst performing on EPYC.
Also notice the fact that the low IPC omnetpp ("network sim") runs slower on Skylake-SP than on Broadwell, but still much faster than AMD's EPYC. Omnetpp is an application that benefited from the massive 55 MB L3-cache of Broadwell, and that is why performance has declined on Skylake. Of course, this also means that the fractured 8x8 MB L3 of AMD's EPYC processor causes it to perform much slower than the latest Intel server CPUs. In the video encoding benchmark "h264ref" this plays a role too, but that benchmark relies much more on DRAM bandwidth. The fact that the EPYC core has higher DRAM bandwidth available makes sure that the AMD chip does not fall too far behind the latest Intel cores.
All in all, we think we can conclude that the single threaded performance of the "Zen architecture" is excellent, but it somewhat let down by the lower turbo clock and the "smaller" 8x8 MB L3-cache.
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JohanAnandtech - Friday, July 21, 2017 - link
Thanks! It is was a challenge, and we will update this article later on, when better kernel support is available.serendip - Tuesday, July 11, 2017 - link
What idiot marketroid thought it was cool to have a huge list of SKUs and gimped "precious metals" branding? I'd like to see Epyc kicking Xeon butt simply because AMD has much more sensible product lists and there's not much gimping going on.ParanoidFactoid - Tuesday, July 11, 2017 - link
Reading through this, the takeaway seems thus. Epyc has latency concerns in communicating between CCX blocks, though this is true of all NUMA systems. If your application is latency sensitive, you either want a kernel that can dynamically migrate threads to keep them close to their memory channel - with an exposed API so applications can request migration. (Linux could easily do this, good luck convincing MS). OR, you take the hit. OR, you buy a monolithic die Intel solution for much more capital outlay. Further, the takeaway on Intel is, they have the better technology. But their market segmentation strategy is so confusing, and so limiting, it's near impossible to determine best cost/performance for your application. So you wind up spending more than expected anyway. AMD is much more open and clear about what they can and can't do. Intel expects to make their money by obfuscating as part of their marketing strategy. Finally, Intel can go 8 socket, so if you need that - say, high core low latency securities trading - they're the only game in town. Sun, Silicon Graphics, and IBM have all ceded that market.msroadkill612 - Wednesday, July 12, 2017 - link
"it's near impossible to determine best cost/performance for your application. So you wind up spending more than expected anyway. AMD is much more open and clear about what they can and can't do. Intel expects to make their money by obfuscating as part of their marketing strategy.Finally, Intel can go 8 socket, so if you need that - say, high core low latency securities trading - they're the only game in town. Sun, Silicon Graphics, and IBM have all ceded that market."
& given time is money, & intelwastes customers time, then intel is expensive.
Those guys will go intel anyway, but just sayin, there is already talk of a 48 core zen cpu, making 98 cores on a mere 2p mobo.
As i have posted b4, if wall street starts liking gpu compute for prompter answers, amdS monster apuS will be unanswerable.
nils_ - Wednesday, July 19, 2017 - link
98 cores on a 2p mobo isn't quite right if you keep in mind that the 32 core versions already constitute a 4 CPU system, unless AMD somehow manages to get more cores on a single die.nils_ - Wednesday, July 19, 2017 - link
Good analysis, although Sun and IBM are still coming out with new CPUs and at least with IBM there is renewed interest in the POWER ecosystem.eek2121 - Wednesday, July 12, 2017 - link
, but rather AMD's spanking new EPYC server CPU. Both CPUs are without a doubt very different: micro architecture, ISA extentions, <snip>Should be extensions.
intelemployee2012 - Wednesday, July 12, 2017 - link
After looking at the number of people who really do not fully understand the entire architecture and workloads and thinking that AMD Naples is superior because it has more cores, pci lanes etc is surprising.AMD made a 32 core server by gluing four 8core desktop dies whereas Intel has a single die balanced datacenter specific architecture which offers more perf if you make the entire Rack comparison. It's not the no of cores its the entire Rack which matters.
Intel cores are superior than AMD so a 28 core xeon is equal to ~40 cores if you compare again Ryzen core so this whole 28core vs 32core is a marketing trick. Everyone thinks Intel is expensive but if you go by performance per dollar Intel has a cheaper option at every price point to match Naples without compromising perf/dollar.
To be honest with so many Fabs, don't you think Intel is capable of gluing desktop dies to create a 32core,64core or evn 128core server (if it wants to) if thats the implementation style it needs to adopt like AMD?
The problem these days is layman looks at just numbers but that's not how you compare.
sharath.naik - Wednesday, July 12, 2017 - link
Agree, Most who look at these numbers will walk away thinking AMD is doing well with EPYC. The article points out the approach to testing and also states the performance challenges with EPYC, which can be missed who reading this review without the prior review on the older Xeons. For example the Big data test, I bet the newbies will walk away thinking EPYC beats the older XEONS E5 v4, as thats what the graphs show,without ever looking back at the numbers for a single 22 core Xeon e5 v4. So yes, a few back links in the article will be helpful.warreo - Wednesday, July 12, 2017 - link
Not a fanboi of either company, but care to elaborate more? I checked the original Xeon E5 v4 review. It shows that a single Xeon E5 v4 performs about 10% slower than a dual setup. Extrapolating that here, that means the single Xeon E5 v4 setup would be right around 4.5 jobs per day, which would make it roughly 50% slower than the dual Epyc and Xeon 8176.Sure, you could argue perf/dollar is better against a dual Epyc setup...but one could make the same argument against Intel's Skylake Xeons? I also wouldn't expect the performance to scale linearly anyway. Please let me know what I'm missing.