AMD Ryzen Threadripper 3990X

Say hello to the most powerful desktop processor ever.

AMD has been going from strength to strength with successive iterations of its Zen architecture, most recently culminating in the ultra-high end Threadripper 3-series. The entry level 24-core 3960X we reviewed last month decimated Intel’s entire HEDT lineup, and by some margin. The 3970X 32 model is equally impressive. But, the best was yet to come. Hidden away inside a press deck was a tease of the 3990X, a 64 core flagship behemoth that teased unprecedented levels of parallel computational power. It introduces a completely new paradigm to the consumer marketplace. So powerful is the 3990X, it may be too much processor for consumer level software to handle. Or is it? Let’s see what this monstrous CPU can do.

FITTING THEM ALL IN

The basic topology of the 3990X is carried over from its siblings. The 3990X contains no less than nine chiplets which consist of eight 8-core complexes, each of which packs in 32MB of L3 cache, for a total of 256MB. The core complexes (or CCDs) are built on the 7nm process, which is a major reason why such a dense design can be packed into a relatively small package. The CCDs are joined by a central

compare it to enterprise EPYC or Xeon Platinum CPUs, though as you’d expect, testing like this leaves the 3990X in a mostly lonely position atop many of the benchmark charts. But, and this is a very big but, the 3990X is simply too good.

That big ‘but’ is that a lot of software doesn’t perform too well on the 3990X. Even the much cheaper AM4 3950X or 9900K show it a clean pair of heels in workloads that aren’t specifically coded to recognise, let alone take advantage of it. There are many reasons for this. When you consider that most users are using processors with 4 or 8 threads, this isn’t a surprise. It takes a lot of effort to produce a piece of software that scales to anywhere near 128 threads. The 3990X is simply way ahead of the curve. Just a year ago, a 32-core desktop CPU like the 2990WX was unprecedented. Add in other potential issues such as sub-optimal Windows thread allocation, lower boost clocks and a lack of multi-chip-module topology awareness and it’s easy to reach the conclusion that the 3990X is far from a jack of all trades CPU. You can always disable a bunch of the cores with the Ryzen Master software, but doing that partly defeats the purpose of owning the 3990X in the first place.

With software that does support such a massive number of threads, the results are extraordinary. It’s amazing to see the 3990X up to 3x as fast as Intel’s 18-core 10980 XE and up to five times as fast as a 9900K. It’s simply not a fair fight when it comes to properly supported multithreading.

The level to which Windows supports the 3990X is somewhat up in the air as we write this article. We didn’t find any apparent issue, with our Windows Professional installation recognising all 128 threads as a 1P system, but then it’s necessary to compare Windows results to Linux results to be sure. Linux has extensive roots in the enterprise space and has much better high core count awareness.

POWER AND EFFICIENCY

A 64-core processor is bound to be a difficult beast to tame. Idle temperatures in the mid 30s and all core load in the high 70s with our 360mm NZXT Kraken X73 are pretty good, but temperatures tend to jump around quite a bit as different dies see different loads. Investing the time into an appropriate custom fan curve is advised in order to get rid of constant rises and falls in fan speed. AMD deserves credit for engineering 64 cores to run within a 280W power envelope. It also means that per core power efficiency is simply amazing. The 3990X is also multiplier unlocked, though with the unique power demands and cooling requirements of a 64 core chip, overclocking of this CPU is really not recommended unless you have absolutely top shelf custom watercooling. If plan to OC or even simply enable PBO, be prepared to see power and temperature levels rise dramatically.