The AMD Threadripper 2990WX 32-Core and 2950X 16-Core Review
by Dr. Ian Cutress on August 13, 2018 9:00 AM ESTConclusions: Not All Cores Are Made Equal
Designing a processor is often a finely tuned craft. To get performance, the architect needs to balance compute with throughput and at all times have sufficient data in place to feed the beast. If the beast is left idle, it sits there and consumes power, while not doing any work. Getting the right combination of resources is a complex task, and the reason why top CPU companies hire thousands of engineers to get it to work right. As long as the top of the design is in place, the rest should follow.
Sometimes, more esoteric products fall out of the stack. The new generation of AMD Ryzen Threadripper processors are just that – a little esoteric. The direct replacements for the previous generation units, replacing like for like but with better latency and more frequency, are a known component at this point and we get the expected uplift. It is just this extra enabled silicon in the 2990WX, without direct access to memory, is throwing a spanner in the works.
2950X (left) and 2990WX (right)
When some cores are directly connected to memory, such as the 2950X, all of the cores are considered equal enough that distributing a workload is a fairly easy task. With the new processors, we have the situation on the right, where only some cores are directly attached to memory, and others are not. In order to go from one of these cores to main memory, it requires an extra hop, which adds latency. When all the cores are requesting access, this causes congestion.
In order to take the full advantage of this setup, the workload has to be memory light. In workloads such as particle movement, ray-tracing, scene rendering, and decompression, having all 32-cores shine a light means that we set new records in these benchmarks.
In true Janus style, for other workloads that are historically scale with cores, such as physics, transcoding, and compression, the bi-modal core caused significant performance regression. Ultimately, there seems to be almost no middle ground here – either the workload scales well, or it sits towards the back of our high-end testing pack.
Part of the problem relates to how power is distributed with these big core designs. As shown on page four, the more chiplets that are in play, or the bigger the mesh, the more power gets diverted from the cores to the internal networking, such as the uncore or Infinity Fabric. Comparing the one IF link in the 2950X to the six links in 2990WX, we saw the IF consuming 60-73% of the chip power total at small workloads, and 25-40% at high levels.
In essence, at full load, a chip like the 2990WX is only using 60% of its power budget for CPU frequency. In our EPYC 7601, because of the additional memory links, the cores were only consuming 50% of the power budget at load. Rest assured, once AMD and Intel have finished fighting over cores, the next target on their list will be this interconnect.
But the knock on effect of not using all the power for the cores, as well as having a bi-modal operation of cores, is that some workloads will not scale: or in some cases regress.
The Big Cheese: AMD’s 32-Core Behemoth
There is no doubting that when the AMD Ryzen Threadripper 2990WX gets a change to work its legs, it will do so with gusto. We were able to overclock the system to 4.0 GHz on all cores by simply changing the BIOS settings, although AMD also supports features like Precision Boost Overdrive in Windows to get more out of the chip. That being said, the power consumption when using half of the cores at 4.0 GHz pushes up to 260W, leaving a full loaded CPU nudging 450-500W and spiking at over 600W. Users will need to make sure that their motherboard and power supply are up to the task.
This is the point where I mention if we would recommend AMD’s new launches. The 2950X slots right in to where the 1950X used to be, and at a lower price point, and we are very comfortable with that. However the 2950X already sits as a niche proposition for high performance – the 2990WX takes that ball and runs with it, making it a niche of a niche. To be honest, it doesn’t offer enough cases where performance excels as one would expect – it makes perfect sense for a narrow set of workloads where it toasts the competition. It even outperforms almost all the other processors in our compile test. However there is one processor that did beat it: the 2950X.
For most users, the 2950X is enough. For the select few, the 2990WX will be out of this world.
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MattZN - Monday, August 20, 2018 - link
If its idling at 80-85W that implies you are running the memory fabric at 2800 or 3000MHz or higher. Try running the fabric at 2666MHz.Also keep in mind that a 2990WX running all 64 threads with a memory-heavy workload is almost guaranteed to be capped out by available memory bandwidth, so there's no point overclocking the CPU for those sorts of tests. In fact, you could try setting a lower PPT limit for the CPU core along with running the memory at 2666... you can probably chop 50-100W off the power consumption without changing the test results much (beyond the difference between 3000 and 2666).
It's a bit unclear what you are loading the threads with. A computation-intensive workload will not load down the fabric much, meaning power will shift to the CPU cores and away from the fabric. A memory-intensive workload, on the otherhand, will stall-out the CPU cores (due to hitting the memory bandwidth cap that 4 memory channels gives you), and yet run the fabric at full speed. This is probably why you are seeing the results you are seeing. The CPU cores are likely hitting so many stalls they might as well be running at 2.8GHz instead of 3.4GHz, so they won't be using nearly as much power as you might expect.
-Matt
XEDX - Monday, August 20, 2018 - link
What happened to the Chromium compile rate for the 7980XE? On it's own review posted on Sep 25th 2017, it achieved 36.35 compiles per day, but in this review it dropped all the way down to 21.1.jcc5169 - Saturday, August 25, 2018 - link
Intel Will Struggle For Years And AMD Will Reap The Benefits-- SegmentNext https://segmentnext.com/SWAPNALI - Tuesday, August 28, 2018 - link
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Relic74 - Wednesday, August 29, 2018 - link
Regardless of the outcome, I went ahead and bought the 32 Core version. As I run SmartOS, an OS designed to run and manage Virtual Machines, I decided to go this route over the Epyc 24. My setup includes the new MSI MEG X399, 32 Core TR, 128GB DDR4 RAM, 3x Vega Frontier (used, $1000 for all three, no one wants them but I love them), 1 X Nvidia Titan Z (used for only $700, an amazing find from a pawn shop, did not know what he had, had it marked as an XP). Storage is 2 x 1TB Samsung 970 Pro in Raid 0 and 5x 8TB SATA in Raid 5 with 8GB of cache on card.The system is amazing and cost me much, much less than the iMac Pro I was about to buy. Now though, I can run any OS in VM, including OSX, with a designated GPU per VM and cores allocated to them. This setup is amazing, SmartOS is amazing, I have stopped running OS's with every application installed, Instead I create single purpose VM's and just install one or maybe two applications per. So for instance when I'm playing a game like DCS, a fantastic flight simulator, only has DCS and Steam installed on the VM. Allowing for the best performance possible, no, the lost of any performance by running things in VM are so minuscule that it's a none issue. DCS with the Titan V runs at over 200 FPS at 4K with everything turned to their max values. I have to actually cap games to my gaming monitors 144Hz refresh rate. Not only that but I can be playing the most demanding game their is, even in VR, while encoding a media file, while rendering something in Blender, while compiling an application, all tasks running under their own VM like a orchestra of perfection.
Seriously, I will never go back to a one OS at a time machine again, not when SmartOS exists and especially not when 32 Cores are available at your command. In fact, anyone who buys this CPU and just runs one single OS at a time is an idiot as you will never, ever harness it's full intention as no one single application really can at the moment or at least not to the point where it's worth doing it.
Most games dont need more than 4 cores, most design applications can't even use more than 2 cores, rendering applications use more of the GPU than CPU, in fact the only thing that really tasks my CPU is SmartOS that is controlling everything but even that doesn't need more than 6 cores to function perfectly, heck, I even had it at 12 cores but it didn't utilize it. So I have cores coming out of the yin-yang and more GPU's than I know what to do with. Aaaaahhhh poor, poor me.
This computer will be with me for at least 10 years without ever feeling that I need an upgrade, which is why I spent the money, get it right the first time and than leave it alone I say.
Oh and the memory management for SmartOS is incredible, I have set it up where if a VM needs more RAM, it will just grab it from another that isn't using it at the moment, it's all dynamic. Man, I am in love.
Anyway.....
Phaedra - Sunday, March 3, 2019 - link
Hi Relic74,I enjoyed reading your lengthy post on the technical marvel that is SmartOS and the 32 Core TR.
I am very much interested in the technical details of how you got SmartOS to work with AMD hardware. Which version of SmartOS, Windows, KVM (or BHYVE) with PCI passthrough etc?
I am in the process of preparing my own threadripper hyper computer and would love some advice regarding the KVM + PCI passthrough process.
You mention gaming in a VM so I assume that you used a Windows 10 guest via KVM with PCI passthrough?
The following says SmartOS doesn't support KVM on AMD hardware: https://wiki.smartos.org/display/DOC/SmartOS+Techn...
Did you build the special module with amd-kvm support:
https://github.com/jclulow/illumos-kvm/tree/pre-ep...
or
https://github.com/arekinath/smartos-live
I would appreciate any insight or links to documentation you could provide. I am familiar with Windows/Linux/BSD so you can let me have the nitty-gritty details, thanks
gbolcer - Wednesday, September 19, 2018 - link
Curious why virtualization disabled?Ozymankos - Sunday, January 27, 2019 - link
Your tests are typical for a single core machine which is laughableplease try to download a game with steam,play some music,watch tv on a tvtuner card,play a game on 6 monitors or 8 or 4 ,do some work like computing something in the background(not virus scanners,something intelligent like life on other planets)
then you shall see the truth
intel352 - Thursday, July 18, 2019 - link
Old article obviously, but wth, numerous benchmark graphics are excluding 2950x in the results. Pretty bad quality control.EthanWalker28 - Monday, February 24, 2020 - link
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