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.
219 Comments
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extide - Tuesday, July 11, 2017 - link
PCPer made this same mistake -- Nehalem/Westmere used a crossbar memory bus -- not a ringbus. Only Nehalem/Westmere EX used the ringbus (the 6500/7500 series) The i7 and Xeon 5500 and 5600 series used the crossbar.extide - Tuesday, July 11, 2017 - link
Sandy Bridge brought the ringbus down to Xeon EP and client chips.Yorgos - Tuesday, July 11, 2017 - link
"With the complexity of both server hardware and especially server software, that is very little time. There is still a lot to test and tune, but the general picture is clear."No wonder why we see ubuntu and ancient versions of gcc and the rest of the s/w stack.
Imagine if you tried to use debian or rhel, it would take you decades to get the review.
eligrey - Tuesday, July 11, 2017 - link
Why did you omit the Turbo frequencies for the Xeon Gold 6146 and 6144?Intel ARK says that the 6146's turbo frequency is 4.2GHz and the 6144's is 4.5GHz.
eligrey - Tuesday, July 11, 2017 - link
Oops, I mean 4.2GHz for both.boozed - Tuesday, July 11, 2017 - link
Need more Skylake-SP SKUsrHardware - Tuesday, July 11, 2017 - link
For the purley system, It's listed that you used Chipset Intel Wellsburg B0This information cannot be correct. Lewisburg Chipset is the name of the purley chipset. Also, B0 stepping lewisburg also wouldn't boot with the stepping of CPU you have.
rHardware - Tuesday, July 11, 2017 - link
That 0200011 microcode is also very old.Rickyxds - Tuesday, July 11, 2017 - link
I'am a brazilian processors enthusiast and I'am very critic about intel and AMD processors, between 2012 and Q1 2017 AMD just doesn't existed, who bought AMD on that years, bougth just for love AMD and just it, doesn't for the price, doesn't for the high core count, doesn't for AMD is red, AMD was the worst performance processors. The A9 Apple dual core performance is better than FX 8150.But now I am very surprise with the aggressive AMD prices. No one here Imagined get the Ryzen 7 performance for less than $500. And I don't know if this scenario brings profit to AMD, but for the image against the intel it's wonderful.
On the next years we will see.
krumme - Tuesday, July 11, 2017 - link
Thank you for quality stuff article especially given the short time. So thank you for booting up Johan !Interesting and surpricing results.