Three years ago, I build a system with an Intel i7 7700K. Last month, I replaced that Intel with an AMD R7 3800X, which advertised a 4.5GHz speed, but typically delivered about 4.2 for single core loads and 4.0 for all core. That isn't unusual for Ryzen CPU's, where your "up to" speed and your actual speed will vary by 200-300MHz. The single core speed just wasn't enough of an improvement over my old Intel. It also isn't worth my time (or yours) trying to mess with overclock settings when the chip is pretty well optimized out of the box.
Enter the new XT processors. I could have swapped up to the 3800XT, which would have given me the speed bump I wanted, but would have cost $70 more for just that extra MHz. The 3900XT here was $170 more, but delivered 50% more cores as well as the same low-load speed of the lesser XT chip. It's the better value, and likely the more future-proof solution as well, as more software is written to take advantage of high core counts.
So what does this 3900XT do? It does indeed hit the 4.7GHz advertised speed on 2 cores (4766MHz to be exact). It will do this while you're browsing the web or otherwise not doing much. Low-to-Medium use cases (e.g. games) will see the chip turbo up to 4.2-4.5GHz. The heaviest loads will see a boost to 4.0-4.2GHz. The exact number depends on the specific kind of program being run. In general, it's a 5-10% improvement over the 3800X.
Your exact chip will vary a bit from these figures, likely less than 100MHz. It might also depend on your cooling setup. I stuck my 3900XT into a ITX box and a compact heat sink (pictured). More robust cooling and a more aggressive PBO (a built-in overclocking function) could probably net you slightly better performance. Again, on the order of 100-150MHz. So you could, potentially, see 4.7+ top speeds and 4.6 in-game turbos. However, AMD doesn't leave performance hanging out there.
The main thing to consider is why this over the 3900X (no "T") which can be had for $70-100 less. In my case, I was choosing the better binning, the better chance of hitting higher low-thread clocks, and (preferably) lower heat. In short, I wanted a sure bet. The 3900XT delivers. This chip, unless you're hitting all 12 cores with 24 threads, actually runs as cool or cooler than my 3800X.
So if you're looking for a lot of GHz and a lot of cores, and money isn't really an object, get this. There will be something new around the corner (there always is) and at that point, maybe you should get that instead. Right here, right now, there isn't a lot that's better.
| Processor | 4.7 GHz ryzen_9_3900x |
|---|
