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
Memory Subsystem: Bandwidth
Measuring the full bandwidth potential with John McCalpin's Stream bandwidth benchmark is getting increasingly difficult on the latest CPUs, as core and memory channel counts have continued to grow. We compiled the stream 5.10 source code with the Intel compiler (icc) for linux version 17, or GCC 5.4, both 64-bit. The following compiler switches were used on icc:
icc -fast -qopenmp -parallel (-AVX) -DSTREAM_ARRAY_SIZE=800000000
Notice that we had to increase the array significantly, to a data size of around 6 GB. We compiled one version with AVX and one without.
The results are expressed in gigabytes per second.
Meanwhile the following compiler switches were used on gcc:
-Ofast -fopenmp -static -DSTREAM_ARRAY_SIZE=800000000
Notice that the DDR4 DRAM in the EPYC system ran at 2400 GT/s (8 channels), while the Intel system ran its DRAM at 2666 GT/s (6 channels). So the dual socket AMD system should theoretically get 307 GB per second (2.4 GT/s* 8 bytes per channel x 8 channels x 2 sockets). The Intel system has access to 256 GB per second (2.66 GT/s* 8 bytes per channel x 6 channels x 2 sockets).
AMD told me they do not fully trust the results from the binaries compiled with ICC (and who can blame them?). Their own fully customized stream binary achieved 250 GB/s. Intel claims 199 GB/s for an AVX-512 optimized binary (Xeon E5-2699 v4: 128 GB/s with DDR-2400). Those kind of bandwidth numbers are only available to specially tuned AVX HPC binaries.
Our numbers are much more realistic, and show that given enough threads, the 8 channels of DDR4 give the AMD EPYC server a 25% to 45% bandwidth advantage. This is less relevant in most server applications, but a nice bonus in many sparse matrix HPC applications.
Maximum bandwidth is one thing, but that bandwidth must be available as soon as possible. To better understand the memory subsystem, we pinned the stream threads to different cores with numactl.
| Pinned Memory Bandwidth (in MB/sec) | |||
| Mem Hierarchy |
AMD "Naples" EPYC 7601 DDR4-2400 |
Intel "Skylake-SP" Xeon 8176 DDR4-2666 |
Intel "Broadwell-EP" Xeon E5-2699v4 DDR4-2400 |
| 1 Thread | 27490 | 12224 | 18555 |
| 2 Threads, same core same socket |
27663 | 14313 | 19043 |
| 2 Threads, different cores same socket |
29836 | 24462 | 37279 |
| 2 Threads, different socket | 54997 | 24387 | 37333 |
| 4 threads on the first 4 cores same socket |
29201 | 47986 | 53983 |
| 8 threads on the first 8 cores same socket |
32703 | 77884 | 61450 |
| 8 threads on different dies (core 0,4,8,12...) same socket |
98747 | 77880 | 61504 |
The new Skylake-SP offers mediocre bandwidth to a single thread: only 12 GB/s is available despite the use of fast DDR-4 2666. The Broadwell-EP delivers 50% more bandwidth with slower DDR4-2400. It is clear that Skylake-SP needs more threads to get the most of its available memory bandwidth.
Meanwhile a single thread on a Naples core can get 27,5 GB/s if necessary. This is very promissing, as this means that a single-threaded phase in an HPC application will get abundant bandwidth and run as fast as possible. But the total bandwidth that one whole quad core CCX can command is only 30 GB/s.
Overall, memory bandwidth on Intel's Skylake-SP Xeon behaves more linearly than on AMD's EPYC. All off the Xeon's cores have access to all the memory channels, so bandwidth more directly increases with the number of threads.
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tmbm50 - Wednesday, July 12, 2017 - link
Windows licensing is irrespective of virtualization.If you run a vm with a single vCPU on a server with 32 cores, you must license all 32 cores. KVM, ESXi...doesnt matter.
I'm sure most folks ignore that point in the license but if your an enterprise and get audited it's enforced.
nils_ - Wednesday, July 19, 2017 - link
Oracle does the same, and if your environment supports migration to other hosts you'd have to license those too (just in case). It's sort of criminal really.pepoluan - Friday, July 28, 2017 - link
I wonder, though, how does AWS managed to offer per-instance Windows licensing for EC2?Because, by that logic, EVERY Windows instance needs to be licensed against ALL cores in an Availability Zone...
Rοb - Sunday, July 23, 2017 - link
From very brief research it looks like for you're in for $6K per 16 Cores for the Datacenter Edition, trying to run the Software on a 4S 32 Core would cost 64x as much (excluding any Bulk Buy pricing you might be able to request).If you bought SM Fat Twins everything would be separated with less loss of density; for the money saved on Licensing would it pay off.
You want to conduct your business lawfully and can charge the customer what it costs plus profit - that's what it costs, want something different the price will probably be different.
Most Software that has per Core Licenses costs a fair bit and has thought it out so someone can't (lawfully) buy a single License and then run the Software on a much more powerful machine.
Take a deep breath and consider that if you ran it on a Phi x200 in x86 Mode that it would run slowly and you'd be charged for 256 Cores per CPU - so don't do that.
I don't want to sound unsympathetic but if the Vendor didn't make money then they wouldn't have incentive to write the Software.
Convince your customers to switch to free Software or for those prices write your own.
What is the complaint exactly, have a Rack Unit Fee, an Electricity Fee, a CPU Fee, a Software Fee, etc., and tell the customer that XYZ costs that much but if they get WYZ it will only cost so much instead.
Assuming everyone obeys the Law and pays the same for Electricity, Cooling, Electronics, Software and Labor then it's only the percentage of Profit where the difference in price lies - or in other words someone will always charge less (and not be 'audited' / as honest / as intelligent and hard working as your Team).
Let the people who you buy your Software from know your complaint and options, we can't be of much more help to you other than the years of service some of us devote to free and pay Software.
rocky12345 - Wednesday, July 12, 2017 - link
Great article as always I found it very well written and there was a lot of information to take in. It was good to see AMD chips doing this good. Bang for the buck seems to be in AMD's court in both the server market and consumer markets now.To those saying oh in the real world big companies would not be upgrading there software to the latest because of money that may be lost. You guys have a solid point there. BUT these tests are not being done in a real world company that depends on their servers to be up 100% of the time. These are just in house tests done to benchmark the new CPU's so yes the latest and greatest versions of the software can be & should be used. This shows exactly what the new CPU's can do when the software is updated to support the latest and greatest hardware. DO you actually think a huge company when buying new server clusters asks for software that is 5 -10 years olds I am fairly sure they do not. They want the most update to date software that is optimized for the new hardware they are spending big bucks on. They want it to be 100% stable and they also want the latest and greatest because of the fact that they probably will never update the software again or at least not for 5-7 years or more. So testing with old builds of software is very unrealistic and does not show the hardware at it's best and also not what a company is looking fro when buying new hardware.
With that said this is still a great write up and deserves a lot of praise.
rahvin - Wednesday, July 12, 2017 - link
I think it's a great comparison article too, you know it's pretty unbiased when both the Intel and AMD fanboi's are out in force criticizing the article for bias.My main comment is that Intel is crazy with those prices on the platinum chips. Those prices are easily two times the previous generation. This is the result of AMD being absent from the server market, that is Intel running processor prices up to the prices that Sun, IBM and HP used to charge in the worst of the enterprise server days. $13k for a Xeon, you've got to be shitting me.
Here's to hoping AMD mops the floor with them and causes prices to crater just like the last time Opteron was competitive. I remember the days when the highest end Xeon was less than $1000. These days the bottom end Xeons are pricing at $1000 and the high ends are 13X that much. Again, I pray AMD can get 25% market share and knock these prices back into reasonable territory. I also hope AMD makes a ton of money and can keep it up with competitive designs (even if it is doubtful because their management is garbage).
Rοb - Sunday, July 23, 2017 - link
Rahvin writes: "$13K for a Xeon ...".There's more to it than that, read the Fine Print; Intel has all kinds of expensive/inexpensive (depending upon your point of view).
See this Comparison: https://ark.intel.com/compare/120498,120499 .
Which is "less expensive":
Intel® Xeon® Platinum 8180M Processor (28 Cores) for $13,011.00
or
Intel® Xeon® Platinum 8156 Processor (4 Cores) for $7,007.00
So which is less 13 or 7 vs. 28 or 4?
You can't just look at one number.
There are other Technical Points, AMD doesn't have: AVX-512, OmniPath 400Gbps, 8-way Motherboards, etc.
If you MUST have what Intel offers then there's only one choice, if you can work around those things and get along with AMD then you're saving money.
If you wanted bleading edge performance then you'd be looking at Spark or Power; some complain that would deny the ability to play Crysis (and that due to their importance people stay up worrying about their issues).
Which is "best" is often easy to say given a narrow definition, which is best in every possible circumstance can be more of a challenge.
Disclaimer: I don't work at either place and intend to buy Epyc 7nm.
hahmed330 - Wednesday, July 12, 2017 - link
Jolly Good! AMD just smoked Intel's bacon!Impressive showing! Outstanding just outstanding!
Shankar1962 - Wednesday, July 12, 2017 - link
Yeah thats why AMD is still in losses and Intel is making net profits of ~$11billion plus each yearThey are gaining share by trying to sell their so called top products for cheap prices
Wondering who is getting smoked
PixyMisa - Thursday, July 13, 2017 - link
Epyc has been out for three weeks.