Investigating Performance of Multi-Threading on Zen 3 and AMD Ryzen 5000
by Dr. Ian Cutress on December 3, 2020 10:00 AM EST- Posted in
- CPUs
- AMD
- Zen 3
- X570
- Ryzen 5000
- Ryzen 9 5950X
- SMT
- Multi-Threading
Gaming Performance (Discrete GPU)
For our gaming tests, we are using our AMD Ryzen 9 5950X paired with an NVIDIA RTX 2080 Ti graphics card. Our standard test suite consists of 12 titles, tested at four configurations:
- Stage 1: Actual Gaming (1080p Maximum Quality, or equivalent)
- Stage 2: All About Pixels (‘4K Minimum’ Quality)
- Stage 3: Medium Low (‘1440p Minimum’)
- Stage 4: Lowest Lows (720p Minimum or lower)
The final three settings are a set of CPU-limited gaming, and help find the limit of where we move from CPU limited to GPU limited. Some users baulk at this testing finding it irrelevant, however these configurations have been widely requested over the years. The contraire to this testing is the first setting, at 1080p Maximum: this being requested given that 1080p is the most popular gaming resolution, and Maximum Quality because this graphics card should be able to handle almost everything at that resolution at very playable framerates.
All the details for our gaming tests can be found in our #CPUOverload article.
Stage 1: Actual Gaming AMD Ryzen 9 5950X, SMT On vs SMT Off |
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AnandTech | Settings | Average FPS |
95th Percentile |
Chernobylite | 1080p Max | 100% | - |
Civilization 6 | 1080p Max | 103% | - |
Deus Ex: MD | 1080p Max | 99% | 100% |
Final Fantasy 14 | 1080p Max | 102% | - |
Final Fantasy 15 | 8K Standard | 100% | 99% |
World of Tanks | 1080p Max | 100% | 102% |
World of Tanks | 4K Max | 103% | 102% |
Borderlands 3 | 1080p Max | 101% | 103% |
F1 2019 | 1080p Ultra | 103% | 106% |
Far Cry 5 | 1080p Ultra | 104% | 104% |
GTA V | 1080p Max | 99% | 100% |
RDR 2 | 1080p Max | 100% | 100% |
Strange Brigate | 1080p Ultra | 101% | 101% |
In real-world gaming situations, there’s very little to pick between having SMT enabled or disabled. Almost universally it is either beneficial or a smidgen better to have it enabled, with F1 2019, Civilization 6, and Far Cry 5 seemingly the best recipients. I’ve also added in the Stage 3 result from World of Tanks, just because that benchmark doesn’t really have a proper settings menu.
Stage 2: All About Pixels AMD Ryzen 9 5950X, SMT On vs SMT Off |
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AnandTech | Settings | Average FPS |
95th Percentile |
Chernobylite | 4K Low | 99% | - |
Civilization 6 | 4K Min | 105% | - |
Deus Ex: MD | 4K Min | 98% | 100% |
Final Fantasy 14 | 4K Min | 102% | - |
Final Fantasy 15 | 4K Standard | 100% | 100% |
Borderlands 3 | 4K Very Low | 101% | 104% |
F1 2019 | 4K Ultra Low | 100% | 100% |
Far Cry 5 | 4K Low | 101% | 100% |
GTA V | 4K Low | 100% | 101% |
RDR 2 | 8K Min | 100% | 100% |
Strange Brigate | 4K Low | 100% | 100% |
With our high resolution settings with minimal quality, there is only one outlier in Civilization 6 on the average frame rates, which seem to be a bit higher when SMT is enabled.
Stage 3: Medium Low AMD Ryzen 9 5950X, SMT On vs SMT Off |
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AnandTech | Settings | Average FPS |
95th Percentile |
Chernobylite | 1440p Low | 100% | - |
Civilization 6 | 1440p Min | 105% | - |
Deus Ex: MD | 1440p Min | 97% | 96% |
Final Fantasy 14 | 1440p Min | 102% | - |
Final Fantasy 15 | 1080p Standard | 101% | 105% |
World of Tanks | 1080p Standard | 101% | 101% |
Borderlands 3 | 1440p Very Low | 103% | 105% |
F1 2019 | 1440p Ultra Low | 99% | 99% |
Far Cry 5 | 1440p Low | 99% | 99% |
GTA V | 1440p Low | 100% | 99% |
RDR 2 | 1440p Low | 100% | 100% |
Strange Brigate | 1440p Low | 100% | 100% |
At the more medium settings, we’re starting to see some more variation (Borderlands gets a few percent from SMT). We’re starting to see Deus Ex:MD drop off a bit with SMT enabled.
Stage 4: Lowest Lows AMD Ryzen 9 5950X, SMT On vs SMT Off |
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AnandTech | Settings | Average FPS |
95th Percentile |
Chernobylite | 360p Low | 106% | - |
Civilization 6 | 480p Min | 102% | - |
Deus Ex: MD | 600p Min | 91% | 91% |
Final Fantasy 14 | 768p Min | 102% | - |
Final Fantasy 15 | 720p Standard | 99% | 102% |
World of Tanks | 768p Min | 101% | 100% |
Borderlands 3 | 360p Very Low | 108% | 110% |
F1 2019 | 768p Ultra Low | 102% | 105% |
Far Cry 5 | 720p Low | 100% | 101% |
GTA V | 720p Low | 99% | 98% |
RDR 2 | 384p Low | 100% | 103% |
Strange Brigate | 720p Low | 95% | 95% |
This is perhaps our most varied set of results, with Deus Ex:MD showing an almost 10% drop with SMT enabled. DEMD is usually considered a CPU title, but so is Chernobylite, which sees a 6% gain. Borderlands is +8-10% with SMT enabled, which is more of a modern game. However, I doubt anyone is playing at these resolutions.
Overall Gaming Performance
If we take full averages from all the data points, then we’re seeing a rough +1% gain in performance in the more complex scenarios across the board.
Resolution Average Comparison AMD Ryzen 9 5950X, SMT On vs SMT Off |
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AnandTech | Setting | aka | Average FPS |
95th Percentile |
Stage 1 | 1080p Max | Actual Gaming | 101% | 101% |
Stage 2 | 4K+ Min | All About Pixels | 101% | 101% |
Stage 3 | 1440p Min | Medium Lows | 101% | 101% |
Stage 4 | < 768p Min | Lowest Lows | 100% | 101% |
In reality, any loss or gain is highly dependent on the title in question, and can swing from one side of the line to the other. It’s clear that Deus Ex prefers SMT off, and F1 2019 or Borderlands prefers SMT on, but we are talking fine margins here.
126 Comments
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CityBlue - Thursday, December 3, 2020 - link
Sure, there are numerous examples of non-core silicon in x86 environments that are insecure, however this article is about SMT yet it avoids mentioning the ever growing list of security problems with Intels implementation of SMT. The Intel implementation of SMT is so badly flawed from a security perspective that the only way to secure Intel CPUs is to completely disable SMT, and that's the bottom line recommendation of many kernel and distribution developers that have been trying to "fix" Intel CPUs for the past few years.abufrejoval - Thursday, December 3, 2020 - link
I use an Intel i7 in my pfSense firewall appliance, which based on BSD.BSD tends to remind you, that you should run it with SMT disabled because of these side channel exposure security issues.
Yet, with the only workload being pfSense and no workload under an attacker's control able to sniff data, I just don't see why SMT should be a risk there, while extra threads to deeply inspect with Suricata should help avoiding that deeper analysis creates a bottleneck in the uplink.
You need to be aware of the architectural risks that exist on the CPUs you use, but to argue that SMT should always be off is a bit too strong.
Admittedly, when you have 16 real cores to play with, disabling SMT hurts somewhat less than on an i3-7350K (2C/4T), a chip I purchased once out of curiosity, only to have it replaced by an i5-7600K (4C/4T) just before Kaby Lake left the shelves and became temptingly cheap.
It held up pretty well, actually, especially because it did go to 4,8 GHz without more effort than giving it permission to turbo. But I'm also pretty sure the 4 real cores of the i5-7600k will let the system live longer as my daughter's gaming rig.
CityBlue - Thursday, December 3, 2020 - link
> to argue that SMT should always be off is a bit too strong.Not really - if you're a kernel or distro developer then Intel SMT "off" is the only sane recommendation you can give to end users given the state of Intel CPUs released over the last 10 years (note: the recommendation isn't relating to SMT in general, not even AMD SMT, it is only Intel SMT).
However if end users with Intel CPUs choose to ignore the recommendation then that's their choice, as presumably they are doing so while fully informed of the risks.
leexgx - Saturday, December 5, 2020 - link
The SMT risk is more a server issue then a consumer issueschujj07 - Thursday, December 3, 2020 - link
This article wasn't talking about Intel's implementation, only SMT performance on Zen 3. If this were about SMT on Intel then it would make sense, otherwise no.CityBlue - Thursday, December 3, 2020 - link
The start of the article is discussing the pros and cons of SMT *in general* and then discusses where SMT is used, and where it is not used, giving examples of Intel x86 CPUs. Why not then mention the SMT security concerns with Intel CPUs too? That's a rhetorical question btw, we all know the reason.schujj07 - Friday, December 4, 2020 - link
Since this is an AMD focused article, there isn't the side channel attack vector for SMT. Therefore why would you mention side channel attacks for Intel CPUs? That doesn't make any sense since Intel CPUs are only stated for who uses SMT and Intel's SMT marketing name. Hence bringing up Intel and side channel attack vectors would be including extraneous data/information to the article and take away from the stated goal. "In this review, we take a look at AMD’s latest Zen 3 architecture to observe the benefits of SMT."mode_13h - Sunday, June 6, 2021 - link
> The Intel implementation of SMT is so badly flawed from a security perspective that> the only way to secure Intel CPUs is to completely disable SMT
That's not true. The security problems with SMT are all related to threads from different processes sharing the same physical core. To this end, the Linux kernel now has an option not to do that, since it's the kernel which decides what threads run where. So, you can still get most of the benefits of SMT, in multithreaded apps, but without the security risks!
dotjaz - Thursday, December 3, 2020 - link
Windows knows how to allocate threads to the same CCX (after patches of course). It not only knows the physical core, it also knows the topology.leexgx - Saturday, December 5, 2020 - link
A lot of people forget to install the amd chipset drivers witch can result in some small loss of performance (but also need bios to be kept upto date as well Co compleat the ccx group support and best cores support to advertise to windows