Do You Really Need 32 Cores?

The arms race between AMD and Intel finds the companies regularly increasing the number of cores for their respective lineups. AMD fired the first salvo on the high end desktop with its first-gen Threadripper products that set a new high watermark of 16 cores, but Intel returned fire with beefy 18-core Skylake-X models. Those hefty processors came bearing stratospheric prices and already push far beyond the necessary for all but the most intense users, but now AMD has escalated the battle with 32-core 64-thread Threadripper 2 processors.

The new processors are impressive halo products, and while they appeal to our desire for more of everything, some software isn't optimized for massive multi-core processors.

Do you want 32 cores? Yes. But do you really need them? Well, that depends.

Productivity

Productivity applications are the real target for Intel's Skylake-X and AMD's Threadripper processors. These chips straddle the line between professional workstation-class products, like Intel's Xeon W line, and the upper end of the desktop PC stack. AMD's processors also support ECC memory, which detects and corrects errors automatically to help ensure data integrity, further cementing the value for professionals and semi-professionals.

AMD splits its new Threadripper 2 processors into X and WX families. The X models come with up to 16 cores and 32 threads and are designed for enthusiasts and gamers. The WX models stretch up to 32 cores and 64 threads and appeal to "creatives" and "innovators," like the streamers and video producers of the world. Intel positions its Skylake-X processors for all types of applications.

Applications generally segment into two categories: applications that respond best to per-core performance, which is a mixture of IPC (Instructions per Cycle) and frequency, and parallelized applications that can leverage the full multi-threaded heft of processors with high core counts. Other factors, such as memory and cache throughput and latency, also have varying levels of importance with different workloads.

As we can see, the Threadripper X-series processors generally perform best in multi-threaded applications and offer acceptable performance in lightly-threaded applications, while Intel's lineup excels at lightly threaded workloads but also responds well to threading.

The impact of more cores in threaded workloads, like rendering, compression/decompression, ray tracing, and video processing, is nothing short of explosive, regardless of the company producing them. The speed-up in time-intensive tasks is worth every penny for professionals and semi-professionals alike. The extra cores also facilitate using multiple intense applications simultaneously, which again boosts productivity.

Most lightly-threaded tasks, like basic office software, web browsers, and Adobe software, continue to perform better on mainstream desktop processors. That's a byproduct of their generally-higher frequencies. But the high end processors still offer more than acceptable levels of performance in these tasks, so you don't have to make serious trade-offs in those types of applications to access the benefits of core-heavy processors.

AMD's WX-series processors, which includes the 32-core 64-thread 2990WX, fall into their own unique category. Aside from the industry-leading number of cores, the processors also have a totally unique design that does involve some trade-offs. The design has a distributed memory architecture that leaves half of the cores stranded from local memory, which can lead to reduced performance scaling in some types of applications. In some workloads, like HandBrake, the 32-core beast only provides small advantages over its 16-core counterparts. The processor also lags its competitors in lightly-threaded applications, like web browsers.

But where the Threadripper 2990WX shines, it really shines. Heavy multi-threaded applications like rendering, decompression, and ray tracing, see massive performance gains that easily dwarf the competition. This product serves a very specific niche of the workstation segment, but it can offer tangible benefits if your workload can exploit the extreme parallelism.

Gaming

AMD doesn't specifically target the gaming market with its higher-end WX series chips, instead cutting its gaming recommendation off at the 16-core 32-thread Threadripper 2950X.

Conversely, Intel recommends its competing Skylake-X models, which feature up to 18 cores, for gaming and other types of applications. That means Intel defines the cutoff point for gaming at 18 cores, which also happens to be the highest core count in the company's desktop product stack.

Unfortunately, most game titles respond best to lightly-threaded performance, meaning that very few processor cores are actually active while you play most popular titles. Higher core count processors tend to have lower overall frequencies due to thermal limitations, which leads to less performance in some game titles.

AMD's mission to boost the average number of cores has led more developers to optimize game engines for higher core counts, but the reality is that most games still perform best on mainstream processors that top out at eight cores. Our recent experimentation reveals that game engines alone do not bear all of the blame for mediocre performance gains, or at times reduced performance, that stem from processors with extreme core counts.

A recent report from Golem.de outlined abnormal performance regressions with Nvidia video cards paired with AMD's new 32-core Threadripper 2990WX. We updated a test system to the latest version of Windows and the newest graphics drivers from AMD and Nvidia to see if we could replicate the results. Here we can see that the Nvidia GeForce 1080 FE paired with a 16-core Threadripper 2950X, which we've effectively turned into an eight-core processor by toggling AMD's game mode, beats the RX Vega 64 in most game titles.

That's expected. However, running the same tests with the full heft of the 32-core Threadripper 2 2990WX unveils some interesting performance regressions with the Nvidia card that allow Vega card to take an abnormally large lead. We aren't sure of the root cause of these performance regressions. The odd tendencies don't impact all titles, but we have pinged Nvidia for comment. Regardless, this highlights that both drivers and game engines need more optimization to exploit the sheer grunt power of these multi-core beasts, particularly when they are used in tandem with AMD's unique architecture on the WX-series chips. 

Zooming out to a broader set of processors reveals that models with heavy core counts do not perform as well as the less-expensive mainstream processors. Our first two slides contain a geometric mean of frame rates for all of the games in our standard test suite. We split these values into average frame rates and 99th-percentile frame rates, with the latter being a good indicator of the smoothness of your gaming experience. The remainder of the slides contain the results of each test.

We tested all Threadripper models with AMD's recommended "game mode," which essentially transforms them into eight-core sixteen-thread processors. AMD recommends reducing the Threadripper processors' core count because of excessive memory latency borne of the multi-chip module design. This indicates that AMD's higher core counts don't benefit most game titles.

The $2,000 Core i9-7980XE lags the $360 Core i7-8700K in the 99th percentile frame rate measurements. The Core i9-7980XE leads by 1.6 FPS in average frame rates, but you have to pay an extra $1,640 for a minuscule performance advantage -- and that's before we take motherboard costs into account. The overclocked Skylake-X models do lead our charts, but we did not include overclocked results for our mainstream processors due to chart constraints. The mainstream processors would lead the charts after tuning, so they definitely offer the best performance for gaming.

We see the same trend with AMD's eight-core Ryzen 7 2700X. At stock settings, this $329 processor handily dispatches its beefier $1,700 Threadripper 2990WX and $800 2950X counterparts.

Do You Need 32 Cores?

The extra cores from AMD and Intel will come in handy for streamers and heavy multitaskers during gaming sessions, but we don't recommend high-end desktop processors for most gamers. You can achieve better performance with mainstream processors and save quite a bit of money in the process. That leaves more money in the budget for high-performance additives, like a faster GPU or SSD.

We can’t overstate the advantage of more cores in many common productivity applications. If you regularly edit videos, large batches of photos, or do rendering work, the extra cores equate to less time spent waiting on the workloads to complete. That, in turn, allows you to move on to the next task faster.

The 32-core Threadripper 2990WX is nothing short of phenomenal in workloads that can utilize its arsenal of execution cores. Rendering is a good example. But it doesn't scale well in other applications. Unless you have very specific workloads that can utilize the power of 32 cores paired with the unique memory layout, it is best to stick with a more reasonable helping of cores. For now, the rational cutoff point for most users focused on productivity applications or extreme multitasking lands at 18 cores for Intel models and 16 cores for AMD processors.

MORE: AMD Ryzen Threadripper 2 vs. Intel Skylake-X: Battle of the High-End CPUs

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