External GPUs aren't a new concept, but they've certain been overlooked over the years. Recently, though, there's be a bit of a resurgence for this concept, especially thanks to the rise of handheld gaming PCs.

Traditionally, eGPUs have used Thunderbolt to communicate with a computer thanks to the fairly high bandwidth available through PCIe tunneling. However, more recently, we've seen the rise of a new connector called OCuLink.

OCuLink, short for "Optical-Copper Link" offers much higher PCIe bandwidth compared to Thunderbolt, at least on paper. OCuLink, can support up to 16GB/s of bandwidth, though most current implementations seem to only support around 8GB/s (or 64Gbps). Meanwhile, Thunderbolt 4 has 40Gbps, or around 5GB/s. But what does that look like in real life? I wanted to find out.

The setup

Laying some ground rules

Equipment with OCuLink support is hard to come by, so my options for testing this were limited. For these tests, the external GPU I used was the ONEXPLAYER ONEXGPU, and initially, I ran the tests with the ONEXPLAYER X1 gaming handheld. Both of these devices have OCuLink ports, though no cables are included with either. So I got this cable off of Amazon Spain for the purposes of this test.

I had heard from another reviewer that the OCuLink bandwidth on the One Xplayer X1 is actually terrible, so recently, I got to test this with another PC, the Minisforum AtomMan X7 Ti. This mini PC also has both USB4 and OcuLink ports, and as I found out, it works much better. I've preserved the original testing below, but the numbers from the AtomMan X7 Ti are much more interesting.

Running benchmarks

OCuLink is definitely faster

First, let's look at synthetic benchmarks to judge the speed of the OCuLink connection. 3DMark includes a PCIe bandwidth test, which lets us see just how much data is pushed through the GPU on both connection types. Here are the results for both PCs:

It's immediately obvious that OCuLink provides a noticeable uplift in bandwidth compared to USB4/Thunderbolt, but what's even more apparent is just how bad the ONEXPLAYER X1 is when it comes to its OCuLink connection. While it only gets only a roughly 39% uplift over OCuLink, the AtomMan X7 Ti gets closer to a 177% increase in bandwidth. That's a huge gap.

However, when we turn to actual performance in more realistic scenarios, those differences in bandwidth aren't as noticeable. I tried running PCMark 10 on both devices, as well as 3DMark Time Spy Extreme on the ONEXPLAYER X1 and 3DMark Steel Nomad on the Minisforum Atomman X7 Ti:

There are some gains to be had here, and the difference is definitely a bit bigger when we use the Minisforum AtomMan G7 Ti and its much better bandwidth. But the effects on performance overall probably won't be a huge game changer, at least not for every title.

Gaming

Of course, what really matters is testing performance in real games. For that, I ran Forza Horizon 5 and Shadow of the Tomb Raider in their respective benchmark modes, and I tried to play some Elden Ring as well. I measured performance using OCAT, and my colleague Adam Conway graciously graphed the performance charts for me.

On the ONEXPLAYER X1

​​​​​For my testing with the ONEXPLAYER X1 I had the GPU directly connected to my 4K TV, so that it would benefit from directly outputting through the GPU, rather than using the built-in display which is powered by the integrated GPU.

Shadow of the Tomb Raider

Starting with Shadow of the Tomb Raider, we can already see a relatively small but noticeable benefit in terms of performance. OCuLink is consistently faster, and frametimes are more consistent, so you're less likely to see stutters.

To visualize this a bit more clearly, here's what the 99% percentile and 99.9% percentile frametimes look like:

Essentially, this means you'll get a slightly higher frame rate most of the time using OCuLink, but more importantly, you won't notice as many sudden stutters, so the experience will feel way smoother in general.

Forza Horizon 5

In Microsoft's Forza Horizon 5, OCuLink's advantages are even clearer. The game consistently ran at a much higher framerate overall, and the experience clearly benefitted from OCuLink. Weirdly enough, there is one huge spike in frame times, though it appears to be for a single frame. That's still not ideal, but considering it's not a consistent issue at all, this may have been an off-shoot. You're looking at much better performance overall, and that can't be understated.

Here are the percentile frametimes as well:

This means the benchmark ran consistently at around 60FPS using OcuLink, while it was closer to 30FPS on USB4.

Elden Ring

Elden Ring doesn't include a benchmark mode, so for this, I had to test while actually playing the game. I can't perfectly recreate the conditions of the gameplay in each situation, and I also recorded for very different lengths, so these numbers aren't the best possible comparison.

However, in the graph above, you can see very clearly that the frametimes are much lower using OCuLink, and a little more consistent as well. Using USB4, they're all over the the place. The experience is definitely smoother using OCuLink, and for what it's worth, I did far better at defeating enemies in the game while playing on OCuLink compared to USB4. It may be a coincidence, of course, but it does line up with what we're seeing here.

I'll include the percentile frametimes below, but again, keep in mind that the data set for USB4 is much larger here, so you can't consider the tests completely equal.

Either way, it's clear the OCuLink does provide some noticeable benefits.

On the Minisforum AtomMan X7 Ti

My testing with the Minisforum AtomMan X7 Ti was slightly different, as I just used my computer monitor, which is a Quad HD 120Hz display. These results shouldn't be directly compared with the ones above, but rather just between themselves in terms of comparing USB4 and OCuLink.

Shadow of the Tomb Raider

Similar to what we see on the ONEXPLAYER X1, Shadow of the Tomb Raider runs consistently faster when using OCuLink, but the differences are fairly small. Frametimes are lower and more stable, so the experience will definitely be a bit smoother, but not by a huge difference. It looks like the extra OCuLink bandwidth isn't resulting in a huge difference compared to the ONEXPLAYER X1. It's possible that this is because of the lower render resolution resulting in a lesser need for high-resolution textures.

Here are the 99% and 99.9% percentiles for reference:

Forza Horizon 5

The story is a bit different with Forza Horizon 5. Here, the computer performed much better when using the OCuLink connection. You can see in the graph that frametimes are consistently lower, and there are far fewer spikes, too. The difference becomes even more obvious when you look at the percentiles as rawe numbers:

This is a legitimately huge difference, and it shows that the difference in performance will greatly depend on the game you're playing.

Elden Ring

Finally, we have Elden Ring, where I somehow got the same error with the frame rate recorder capturing a much longer period when using USB4 compared to OCuLink. It should be mentioned that the app is set to record over a set amount of time, so I have no control over what's happening here.

Regardless, the results are extremely clear. When running over OCuLink, Elden Ring ran much faster and more smoothly. Frametimes are way slower, and while they still go up and down a bit, it's still much smoother and makes for a more pleasant experience. Here are the percentiles:

Considering Elden Ring is locked at 60FPS, some of the higher numbers here may be because of spikes in framerates during loading screens (such as after a death in the game). Regardless, it's obvious that performance is leagues better over the OCuLink connection.

Is OCuLink worth it?

Just looking at the rresults we got here, it's clear to see that OCuLink can provide a far better experience in some games thanks to that additional PCIe bandwidth. Forza Horizon 5 seems to benefit the most from it out of the titles we tested, but the experience was better across the board, even if a title like Shadow of the Tomb Raider only showed a minimal difference.

But performance isn't everything, and an important factor to consider here is availability. OCuLink is not a very common connector, and finding both a PC and a GPU with the port will severely limit your options, meaning you may end up spending more or buying from a more obscure brand.

Thunderbolt 5 is starting to appear in some devices, and it's likely going to be far more popular. For that alone, it may be worth waiting to see if new GPU options appear that are more widely supported.