AMD 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 I/O die which is built with the older 12nm process. Overall the CPU packs in over 33 billion transistors. It’s a stunning feat of engineering when you consider that Intel, with all its R&D budget, will be using 14nm monolithic dies for the foreseeable future.
The 3990X operates at a base frequency of 2.9GHz but can boost up to 4.3GHz when thermal and power conditions allow it. You also get 64 PCIe 4.0 lanes, which when combined with those available from the TRX40 chipset, brings it to a total of 72 lanes. All the TRX40 boards seen to date have been especially feature rich. There’s no need to worry about what happens if you populate a lot of different PCIe slots or equip a number of M.2 drives or SATA devices, they will all run together at the same time with very few compromises. The 3990X supports quad channel memory with up to 256 GB possible over eight slots.
WHAT IT’S GOOD FOR – AND NOT
At $6,499, the 3990X CPU is a very expensive CPU, and that means you’ve got every right to expect top level performance to match its price tag. As the 3990X is a desktop CPU, we won’t go and 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 four or eight 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 multichip-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.
The Threadripper 3990X is simply a monster of a CPU, but we recommend it only if you have highly parallel workloads that can make us of its power. A prosumer or ultra-enthusiast will be better served by the likes of a 3970X or 3960X. If you’re a professional who renders, data mines, compiles, prototypes, encodes or runs a load of virtual machines, you’ll already know if the 3990X is right for you. Time is money if you can deliver your completed project that much faster. Feed the 3990X the right work and you’ll be rewarded with unprecedented performance. For the rest of us? Come back in a couple of years when the software has caught up. With 6- and 8-core processors only now going mainstream. It’s going to be a long time before a 64-core processor is truly beneficial for an enthusiast, let alone the average consumer. Still, we love the 3990X and it’s a technological statement par excellence.