I Tried An OCuLink External GPU — Is It Actually Better Than USB4?

Recently, I tried using an external GPU for the first time and found it to be a very useful addition if you want to improve your gaming experience. Games greatly benefit from the added power, so if you’re playing at home, you can make them look a lot better using an external GPU, though the cost is a significant barrier.

But that was all using USB4 (or Thunderbolt), which is the most common connection for external GPUs, since just about every laptop has it. But recently many devices have come with a new port, called OCuLink, specifically designed for external GPUs. 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 looking at product pages like the GPD G1, the bandwidth is around 64Gbps, or 8GB/s. Meanwhile, Thunderbolt 4 has 40Gbps, or around 5GB/s. But what does that look like in real life? I wanted to find out.

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The setup

Laying some ground rules

Equipment with OCuLink support is hard to come by, so my options for testing this were limited. The PC I used was the One XPlayer X1 I recently reviewed, alongside the OneXGPU I used for my previous external GPU tests. 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.

The USB4 tests were run using the same hardware except, of course, the GPU and PC were connected using the included USB4 cable that comes with the OneXGPU.

I have heard from another reviewer that the OCuLink bandwidth on the One Xplayer X1 is actually terrible, so the results here may not necessarily indicate what you can expect from other PCs. I hope to conduct further tests in the future if I get access to another PC with OCuLink.

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Running benchmarks

OCuLink scores higher across the board

Despite the reportedly poor OCuLink bandwidth on the One Xplayer X1, thnings do look a fairly positive when it comes to performance. I started by running some benchmarks, and the most important of these is the 3DMark PCI Express feature. As expected, OCuLink came out on top, but the benefit is smaller than I would have expected considering the OCuLink specs.

That being said, this is a nearly 50% increase in bandwidth, which is still very significant. The benchmark took a good bit longer to run on USB4 due to the lower speeds, too.

I also tried more generic benchmarks, including 3DMark’s Time Spy Extreme and PCMark 10. Here are the results:

Evidently, there are some gains to be had, but they are very small, so I’m inclined to believe the claims that say the One XPlayer X1 has poor OCuLink bandwidth. That being said, an improvement is an improvement, so let’s look at games, too.

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Gaming

Real-life performance is what matters

After these benchmarks, of course, I had to try some gaming to see the effects of this improved bandwidth in real life. 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 had the GPU connected to my TV for this order to benefit from directly outputting through the GPU, rather than using the built-in display which is powered byt he integrated GPU.

I measured performance using OCAT, and my colleague Adam Conway graciously graphed the performance charts for me.

Shadow of the Tomb Raider

Starting with Shadow of the Tomb Raiderwe can already see a relatively small but noticeable benefit in terms of performance, especially with that huge spike in the frametimes that occurred when using USB4 about 70 seconds in. OCuLink was more consistent and faster

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

Essentially, this means you’ll get a slightly smoother experience 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 5OCuLink’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, 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.

Is OCuLink worth it?

Even if the OCuLink bandwidth on the One XPlayer X1 is lacking compared to other devices, there are evidently some big performance gains when using OCuLink compared to USB4. Looking at both benchmarks and actual games, the performance differences are very significant. If you have both a GPU and a computer that already support OCuLink connectivity, investing in an OCuLink cable seems like a no-brainer.

However, based on this data alone, investing in a whole OCuLink ecosystem may be a big ask considering the gains you’re getting here. There’s certainly a chance that other devices will offer better performance over OCuLink, but that doesn’t seem to be the case here, and going out of your way to find PCs and GPUs with OCuLink will severely limit your options.

With Thunderbolt 5 now starting to become available, the benefits of OCuLink will liklely become less obvious, too. Of course, I’m very much looking forward to running more tests with other PCs in the future to see what OCuLink is really capable of.

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