Core i9-9900K vs Ryzen 9 3900X: Which should you buy?

Confused by information overload? Here's what you need to know before you buy AMD or Intel's high-end CPUs

Credit: Adam Patrick Murray/IDG

To outsiders, AMD’s triumphant launch of Ryzen 3000 looks like total victory with the only thing left to do is schedule the ticker-tape parade down Broadway.

Intel, meanwhile, has to look for an impoverished nation to dump a truckload of 2019 CPU Champions shirts onto. 

Fortunately, the truth is a lot more nuanced. And while we’d also name AMD’s Ryzen 3000 the overall champs too —reality requires a lot more context on the CPU that’s right for you.

So to keep you from having to sift through dozens of reviews and hundreds of forum posts, we’ll sum up the strengths and weaknesses of these two power house CPUs and when they’re right for you.

If you do multi-threaded work, buy...Ryzen 3000

This should come of no shock to anyone who has watched AMD’s Ryzen since the beginning. AMD essentially democratized CPU cores with the first Ryzen and hasn’t stopped dragging down the cost per thread ever since. Just to give you an idea: Intel charged $1,723 for the 10-core Core i7-6950X in 2016. That worked out to about $86 per thread. Today, the 12-core Ryzen 9 3900X is $21 per thread.

CPU Per Thread Costs IDG

Per thread costs based on street pricing in June 2019

More cores typically translates into more performance. And more affordable cores, means more performance than ever before. But it all depends on whether you can use those cores or not. Today, it’s mostly 3D animation artists who can use it the most, along with those who do video editing or video encoding. Other multi-threaded apps usually occupy the workstation arena for engineering, scientific or software development. This isn’t always the case (you’d be surprised how many workstation apps don’t use more than a few cores) but when it is, Ryzen 9 is going to be your answer 9 out of 10 times. So hands down, we’d recommend Ryzen over Core for multi-threaded applications.

If you do single-threaded or lightly-threaded work buy...Core i9 or Ryzen 9

We can go ga-ga over the massive amount of cores available today, but the harsh truth is the vast majority of applications still run on a single-core, or just a handful. Even tasks where you’d think more cores would matter, it usually doesn’t. Adobe’s Photoshop, for example, really doesn’t use a lot of cores until you hit certain filters or tasks.

When you take the number of cores out of the equation, it comes down to that old standby of clock speed or megahertz, along with the efficiency of the chip. Efficiency basically denotes how well a CPU uses each clock tick. Obviously, the higher the efficiency and clock speed, the better.

The go-to here is typically Intel, which has had an advantage in efficiency and an advantage in clock speeds over AMD’s older chips. While Intel still has a decent clock advantage, the efficiency of Ryzen has greatly improved. In fact, we’d have to say that it’s mostly a wash these days.

ryzen 9 3900x vs 9900k pbo off mce on thread scaling percentage IDG

For example (above), when we use Cinebench R20 to measure the performance increase of both the Core i9-9900K and Ryzen 9 3900X using 1 thread to 24 threads, you can see the percent difference between the two chips.

We’ve done this kind of comparison before, and typically Intel is better on light (lower thread count) loads, while Ryzen is better on heavier (higher thread count) loads. In this case, AMD’s Ryzen is dominating on the right side of the chart as usual. On the left side, where Ryzen would normally be completely underwater, it’s losing by about 4 to 7 percent, which isn’t much when you consider Intel still has a 400MHz advantage.

So no surprise, it comes down to what you do. Do you prioritize high clocks and CPU efficiency at all cost while not giving a damn about multi-threaded tasks beyond 16-threads? If this is you, then Core i9 is the better choice.

If, however, you actually need boatloads more multi-threading performance, and you’re willing to give up essentially single-digit performance in light and single-threaded loads then Ryzen 9 is the better choice.

Gaming on Ryzen 9 or Core i9: How to choose

When it comes to gaming on high-end CPUs like the Ryzen 9 or Core i9 it’s easy to get confused with the answers you get. That’s because it’s not just about CPU performance, it’s also about how powerful the GPU is, the resolution you play at, and the refresh rate of the monitor.

First, we’ll say that both CPU are absolute great gaming CPUs, and you really can’t go wrong with either. 

And yes nerds, we hear you: If you only play games and don’t need the high-thread count of either chip, a Core i7-9700K (or lower) or Ryzen 7 3700X (or lower) gets you far more bang for your buck.

This story, however, is about folks who need the multi-threaded performance of the Core i9 or Ryzen 9. Core i9 generally leads in gaming performance, but the Ryzen 9 typically trails by very slim single-digit frame rates, so it’s going to be a wash for most folks.

That criterion, however, applies only when playing games in situations where the GPU is not the limiting factor. For example, while the Core i9 outperforms the Ryzen 9, it does that using a GeForce RTX 2080 Ti and at 1080p resolution. If we use a GeForce GTX 1080, it’s mostly a tie. If you tick the resolution up to 2560x1440, it’s a tie as well, even with the 2080 Ti. Playing at 4K? It’s doesn’t really matter which CPU you’re using, because you’re GPU-bound almost all of the time.

If you look at the graphic below, the Core i9’s moment to shine is typically when you absolutely must have the highest frame rates possible. Some have called this use case “eSports,” which is probably a very good choice because eSports generally prioritizes ultra-high frames.

core i9 high refresh with high gpu with low resolution IDG (created on Canva.com)

This should help explain the situations where a Core i9 is likely the better choice over a Ryzen 9 for gaming.

Two factors we didn’t get into that should mentioned is that’s mostly with a conventional gaming experience, without adding streaming into the mix, or what visual quality settings you like to play at.

If you plan to stream video in real time at the highest settings, there’s an argument for the greater core count of Ryzen. Some would say Core i9 performs just as well at the most commonly used streaming settings. Still, we’d give the edge to Ryzen because if you have to edit that video as a streamer, Ryzen's high-thread talents win the day. 

core i9 box amazon toms hardware Tom’s Hardware

Intel has 15,000 developers doing software development out there. Hate it all you want AMD fans, that probably means better performance on Intel chips in applications where you might not expect it.

If you use an app that likes Intel, then, buy Intel

As you try to filter through dozens of reviews and hundreds of forum comments, just remember that you’re buying a CPU for your computer, not their computer. And if you use an application that simply sings on Intel microarchitecture, then your best bet is to stick with Intel. And yes, if you use an app that runs better on AMD CPUs, stick with that.

We only want to point this out because most hardware reviews can really only give you a general sense, which may or may not match your needs and the specific applications that you care about.

If you use Quick Sync...buy Core i9

One ace up Intel’s sleeve has been its Quick Sync support, which is built into Intel CPUs with Intel integrated graphics. Quick Sync is Intel’s fixed function encode support that accelerates video encoding tasks.

The speed difference is stupidly different, as you can see below where we used the x86 CPU cores to encode a video using HEVC vs. using the Quick Sync support in the Core i9.

The short story is if you use a video encoder or video editor with Quick Sync support, it’s worth having it available.

ryzen 9 3900x handbrake 4k mp4 to h265 quicksync IDG

Intel’s QuickSync is insanely fast compared to CPU-based encoding.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Gordon Mah Ung

PC World (US online)
Show Comments

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?