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Closing out this investigation, I have to say some of the results from our eGPU testing are fascinating. I genuinely wasn’t sure if we’d see any performance difference between all four GPUs that we tested. After all, over Thunderbolt 3, we get just four PCIe 3.0 lanes, when the RTX 30-series card are designed for 16 lanes of PCIe 4.0.
What we found was, while the RTX 3090 proved faster than the RTX 3080, and the RTX 3080 proved faster than the RTX 3070 and so on, the margins between all four GPUs we tested are generally smaller than what you’d expect from a desktop system. The RTX 3090 for instance, proved 6-9% faster than the RTX 3080, when we’d expect more like a 10-15% difference using a desktop.
Based on this testing, if I were shopping for a GPU to using in an external Thunderbolt 3 dock, I’d go for either an RTX 3060 Ti or an RTX 3080. In my opinion, when we factor in both CPU and PCIe limitations, neither the RTX 3070 or RTX 3090 are delivering much more performance than the GPUs a step below them.
Then again, if you want to extract every last ounce of performance from a laptop system, it is still pretty impressive that a single Thunderbolt 3 cable will net you more performance with an RTX 3090 than it will with an RTX 3080. You just won't be getting as much more from the RTX 3090 as you would on a desktop.
Considering how much performance is left on the table when using an eGPU compared to using a proper desktop system, using a Thunderbolt 3 enclosure like the EG200 has the most value if you simply have no other option for discrete graphics. Typically that’d be if you have an ultrabook that only has integrated graphics for instance, or perhaps a mini-PC that's also using a mobile processor. Despite being often half as fast than a proper desktop, an eGPU can still deliver a very playable experience in games like Gears 5 and Metro Exodus, though as we saw today, not all games will play nicely with a Thunderbolt 3 dock.
The final point to mention is, if you can, use an external monitor. On average we saw 10-12% better performance using an external monitor than when routing the display signal back to our laptop’s screen. We still saw consistent scaling between all four GPUs even without a monitor, but for maximum performance, it really can make a difference to connect the graphics card to an external monitor.
We don't yet have a buy link for the Cooler Master EG200, but we've been told the MSRP is £329.99.
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KitGuru says: This has been an interesting few days of testing. If you're planning on buying an external GPU enclosure, what machine are you going to connect it to?
