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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edzieba - Monday, August 13, 2018 - link
Not really. In chasing Moar Cores you only excel in embarrassingly parallel workloads. And embarrassingly parallel workloads are in GPGPU's house. And GPU lives in GPGPU's house.boeush - Monday, August 13, 2018 - link
Try to run multiple VMs/Containers and/or multiple desktop sessions on a GPGPU: you might find out that GPGPU's house isn't all it's cracked up to be...SonicKrunch - Monday, August 13, 2018 - link
Look at that power consumption. I'm not suggesting AMD didn't create a really great CPU here, but they really need to work on their efficiency. It's always been their problem, and it's not seemingly going away. The market for these near 2k chips is also not huge in comparison to normal desktop space. Intel has plenty of time to answer here with their known efficiency.The_Assimilator - Monday, August 13, 2018 - link
Yeah... look at the number of cores, numpty.somejerkwad - Monday, August 13, 2018 - link
The same efficiency that has consumer-grade products operating on more electricity in per-core and per-clock comparisons? Overclocking power gets really silly on Intel's high end offerings too, if you care to look at the numbers people are getting with an i9 that has fewer cores.eddman - Monday, August 13, 2018 - link
Interesting, can you post a link, please? I've read a few reviews here and there and when comparing 2600x to 8700k (which is more or less fair), it seems in most cases 8700k consumes less energy, even though it has higher boost clocks.CrazyElf - Monday, August 13, 2018 - link
The 8700k is not the problem. It is Skylake X.https://www.tomshardware.com/reviews/-intel-skylak...
Power consumption when you OC X299 scales up quickly. Threadripper is not an 8700k competitor. It is an X299 competitor. The 32 core AMD is clearly priced to compete against the 7980X, unless Intel cuts the price.
eddman - Tuesday, August 14, 2018 - link
I should've made it clear. I was replying to the "more electricity in per-core and per-clock" part. Also, he wrote consumer-grade, which is not HEDT. I do know that TR competes with SKL-X.Comparing OCing power consumption is rather pointless when one chip is able to clock much higher.
Even when comparing 2950 to 7980, there are a lot of instances where 7980 consumes about the same power or even less. I don't see how ryzen is more efficient.
alpha754293 - Monday, August 13, 2018 - link
@ibnmadhi"It's over, Intel is finished."
Hardly.
For example, the Threadripper 2990WX (32C, 3.0 GHz) gets the highest score in POV-Ray 3.7.1 benchmark, but when you compute the efficiency, it's actually the worst for it.
It consumes more power and only gets about 114 points per (base clock * # of cores - which is a way to roughly estimate the CPU's total processing capability).
By comparison, the Intel Core i9-7980XE (18C, 2.6 GHz) is actually the MOST EFFICIENT at 168 points per (base clock * # of cores). It consumes less power than the Threadripper processors, but it does also cost more.
If I can get a system that can do as much or more for less, both in terms of capital cost and running cost (i.e. total cost of ownership), then why would I want to go AMD?
I use to run all AMD when it was a better value proposition and when Intel's power profile was much worse than AMD's. Now, it has completely flipped around.
Keep also in mind, that they kept the Epyc 7601 processor in here for comparison, a processor that costs $4200 each.
At that price, I know that I can get an Intel Xeon processor, with about the same core count and base clock speed for about the same price, but I also know that it will outperform the Epyc 7601 as well when you look at the data.
As of August, 2018, Intel has a commanding 79.4% market share compared to AMD's 20.6%. That's FARRR from Intel being over.
ender8282 - Monday, August 13, 2018 - link
base clock * number of cores seems like a poor stand in for performance per watt. If we assume that IPC and other factors like mem/cache latency are the same then sure base clock * num cores effectively gives us performance unit of power but we know those are not constant.