64 Cores of Rendering Madness: The AMD Threadripper Pro 3995WX Review
by Dr. Ian Cutress on February 9, 2021 9:00 AM EST- Posted in
- CPUs
- AMD
- Lenovo
- ThinkStation
- Threadripper Pro
- WRX80
- 3995WX
Power Consumption
The nature of reporting processor power consumption has become, in part, a dystopian nightmare. Historically the peak power consumption of a processor, as purchased, is given by its Thermal Design Power (TDP, or PL1). For many markets, such as embedded processors, that value of TDP still signifies the peak power consumption. For the processors we test at AnandTech, either desktop, notebook, or enterprise, this is not always the case.
Modern high performance processors implement a feature called Turbo. This allows, usually for a limited time, a processor to go beyond its rated frequency. Exactly how far the processor goes depends on a few factors, such as the Turbo Power Limit (PL2), whether the peak frequency is hard coded, the thermals, and the power delivery. Turbo can sometimes be very aggressive, allowing power values 2.5x above the rated TDP.
AMD and Intel have different definitions for TDP, but are broadly speaking applied the same. The difference comes to turbo modes, turbo limits, turbo budgets, and how the processors manage that power balance. These topics are 10000-12000 word articles in their own right, and we’ve got a few articles worth reading on the topic.
- Why Intel Processors Draw More Power Than Expected: TDP and Turbo Explained
- Talking TDP, Turbo and Overclocking: An Interview with Intel Fellow Guy Therien
- Reaching for Turbo: Aligning Perception with AMD’s Frequency Metrics
- Intel’s TDP Shenanigans Hurts Everyone
In simple terms, processor manufacturers only ever guarantee two values which are tied together - when all cores are running at base frequency, the processor should be running at or below the TDP rating. All turbo modes and power modes above that are not covered by warranty. Intel kind of screwed this up with the Tiger Lake launch in September 2020, by refusing to define a TDP rating for its new processors, instead going for a range. Obfuscation like this is a frustrating endeavor for press and end-users alike.
However, for our tests in this review, we measure the power consumption of the processor in a variety of different scenarios. These include full AVX2/AVX512 (delete as applicable) workflows, real-world image-model construction, and others as appropriate. These tests are done as comparative models. We also note the peak power recorded in any of our tests.
AMD Ryzen Threadripper Pro 3995WX
The specifications for this processor list 64 cores running at a TDP of 280 W. In our testing, we never saw any power consumption over 280 W:
Going through our POV-Ray scaling power test for per-core consumption, we’re seeing a trend whereby 40% of the power goes to the non-core operation of the system, which is also likely to include the L3 cache.
Red = Full Package, Blue = CPU Core only (minus L3 we think)
We only hit the peak 280 W when we are at 56-core loading, otherwise it is a steady climb moving from 7 W/core in the early loading down to about 3 W/core when fully loaded. What this does for core frequencies is relatively interesting.
Our system starts around 4200 MHz, which is the rated turbo frequency, settling down to 4000-4050 MHz in that 8-core to 20-core loading. After 20 cores, it’s a slow decline at a rate of 25 MHz per extra core loaded, until at full CPU load we observe 3100 MHz on all cores. This is above the 2700 MHz base frequency, but also comes out to 2.86 W per core in CPU-only power, or 4.37 W per core if we also include non-CPU power. Note that non-CPU power in this case might also include the L3.
For an actual workload, our 3DPMavx test is a bit more aggressive than POV-Ray, cycling to full load for ten seconds for each of its six algorithms then idling for a short time. In this test we saw idle frequencies of 2700 MHz, but all-core loading was at least 2900 MHz up to 3200 MHz. Power again was very much limited to 280 W.
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Oxford Guy - Friday, February 12, 2021 - link
Bulldozer was indeed particularly awful. Abstract names like Xeon are generally less annoying than misapplied real-world names.Qasar - Friday, February 12, 2021 - link
too bad bulldozer and netburst were code names for the architecture, and not marketing names like xeon and threadripper.GeoffreyA - Saturday, February 13, 2021 - link
You're right, but even FX and Phenom were in poorer taste than Athlon, which was sheer gold, I'd say. Is Threadripper good or bad as a name? What I say, or anyone else here says, doesn't matter. Only from a survey can we get a better picture, and even there it's a reflection of popular opinion, a blunt instrument, often misled by the times.Is there a standard of excellence, a mode of naming so tuned to the genius of the language that it never changes? It's evident to everyone that "Interstellar" sounds better than "Invisible Invaders from Outer Space," but we could be wrong and time only can decide the matter. If, in 500 years, people still get a shiver when they hear Interstellar, we'll know that Nolan named his film right.
Back to the topic. I think the spirit of Oxford Guy's comment was: TR and Epyc aren't that good names (which I partly agree with). Whether it inspires confidence in professionals is a different matter. A professional might be an expert in their field but it doesn't mean they're an expert on good names (and I'm not claiming I am one either). It matters little: if the target demographic buys, AMD's bank account smiles. But it's a fair question to ask, apart from sales, is a name good or bad? Which were the best? Does it sound beautiful?Names, in themselves, are pleasurable to many people.
jospoortvliet - Saturday, February 13, 2021 - link
Names should have a few properties if they are to be good.Easy to pronounce (cross-culturally!)
Easy to remember (distinctive)
Not (too) silly/funny
Bonus: have some (clever) relation to the actual product.
Threadripper certainly earns the bonus but might arguably perhaps maybe lose out on the 3rd ‘silly’ point. However, in that regards i would argue it makes a difference how well it fulfills that rather ambitious title, and as we all know the answer is “very well”. Now if threadripper was a mediocre product, not at all living up to its name, I’d judge different but as it stands I would say it is a brilliant name.
GeoffreyA - Saturday, February 13, 2021 - link
Good breakdown that, to test names against. Simplicity, too, wins the day.GeoffreyA - Saturday, February 13, 2021 - link
"Bulldozer was indeed particularly awful"One of the worst. AMD's place names were good in the K8 era, and the painter ones are doing a good job too.
danjw - Saturday, February 13, 2021 - link
You may not be aware of this, but Threadripper, is actually comes from the 80's fashion fad of ripped clothing. ;-)GeoffreyA - Saturday, February 13, 2021 - link
Well, I like it even more then, being a fan of the 80s.Hulk - Tuesday, February 9, 2021 - link
Is the difference in output quality strictly due to rounding/numerical errors when using GPU vs CPU or are there differences in the computational algorithms that calculate the numbers?Kjella - Tuesday, February 9, 2021 - link
Not in terms of color accuracy, not a problem making 10/12 bit non-linear color from 32 bit linear - even 16 bit is probably near perfect. But for physics engines, ray tracing etc. errors can compound a lot - imagine a beam of light hitting a reflective surface where fractions of a degree means the light bounces in a completely different direction. Or you're modelling a long chain of events that cause compounding errors, or the sum of a million small effects or whatever. But it can also just be that the algorithms are a bit "lazy" and expect everything to fit because they got 64 bits to play with. I doubt that much needs ~1.0000000001 precision, much less ~1.0000000000000000001.