External GPU Dock Wreaks Havoc on RTX 4090 Gaming Performance

RTX 4090 Founders Edition on a External GPU Dock
(Image credit: YouTube - Jarrod'sTech)

If you were thinking about installing an RTX 4090 into your shiny new external GPU box, you might want to reconsider. JarrodsTech on YouTube recently released a new video showcasing what the RTX 4090 can do with an external Thunderbolt GPU dock connected to a laptop. The results were incredibly bad. In his testing, the dock/laptop combo crippled the 4090's gaming performance, with most games barely being able to use 50% of its power, at best.

For testing, Jarrod used two different laptops: an Asus Zenbook 14 OLED featuring a i7-1260P processor, and a beefier Aorus 17X gaming laptop equipped with a higher-performing Core i9-12900HX. Jarrod also put together a 7950X desktop test rig as a baseline, to see how much performance the 4090 retains in the external GPU dock configuration. This means we have quite a bit of a mismatch in CPU performance between the laptop and desktop PC CPUs, which is important to bear in mind because the RTX 4090 can bottleneck CPUs in some game titles. 

Unfortunately, Jarrod neglected to share details on the external GPU dock he is using, only noting that it's a Thunderbolt 3 dock -- which is good considering most GPU docks today are using Thunderbolt 3. But, Jarrod did switch to an external Corsair 850W power supply for the tests, since the built-in 650W unit didn't have enough 8-pin power connectors for the 4090's quadruple 8-pin power adapter.

In testing, Jarrod found that all titles tested could barely use 50% of the RTX 4090's GPU horsepower, with most being much worse. God of War was one of the best games tested, representing a 35% reduction in performance at 4K on the i7-1260P Zenbook, compared to the desktop 4090 configuration.

But in a worst-case scenario, the external 4090 was up to 82% slower than the desktop counterpart in Watch Dogs Legion at 4K. 

To make matters worse, the performance difference between both laptops was also drastically different in most titles. A good example of this is in Assassin's Creed Valhalla, where the 12900HX gaming laptop was up to twice as slow as the ultrabook with the slower i7-1260P processor.

This game was definitely the worst offender, but many other titles exhibited similar behavior, including Red Dead Redemption 2, Call of Duty Warzone, Watch Dogs Legion, and a couple more.

The behavior is very bizarre, especially when the 12900HX is a significantly faster part. Jarrod suspects the Resizable BAR feature might have something to do with it, but he isn't certain. His 3DMark PCI Express feature tests measured 2.33 GB/s of bandwidth for the TB3 enclosure, and at least some of that shortfall could be due to the eGPU design. However, even at full utilization, the TB3 interface provides far less bandwidth than the 26.85 GB/s he measured with the desktop PC. 

In either case, it seems like pairing an RTX 4090 with a modern-day Thunderbolt 3 GPU dock and a lower-power laptop CPU will result in very poor utilization of the 4090. Thunderbolt 3 GPU docks simply aren't designed to drive a 4090 well, even at 4K resolutions.

We will have to wait for much higher-performing Thunderbolt 4 or (perhaps even Thunderbolt 5) GPU docks before cards like the RTX 4090 make sense as external gaming options. But with the capabilities of high-end GPUs always increasing, thus putting more demand on both the CPU and the external interface, it's unclear if the highest-end GPUs will ever reach similar performance to traditional desktop setups. So for the foreseeable future, it's clear that if you want the best gaming performance possible, you should opt for one of the best gaming PCs or best gaming laptops rather than an external GPU. 

Aaron Klotz
Contributing Writer

Aaron Klotz is a contributing writer for Tom’s Hardware, covering news related to computer hardware such as CPUs, and graphics cards.

  • ManDaddio
    I did not watch Jared's video. I'm just coming out this with my own thoughts on the subject.
    Why would anyone even consider using today's high-end GPUs with a laptop? An RTX 2080 TI, 6800xt,or RTX 3080 should be the maximum performance cards used. And even the latter two would be overkill. Yes I understand people use all kinds of cards with the docking. I'm just coming from a practical stand.
    Also for the price that you pay for the docking station and the card people should just go out and buy a high-end laptop. That would be more practical and efficient.
    I can't say much for Apple users because their choice is very limited. Maybe for them this solution is a solution. But I still wouldn't put today's top tier cards in a docking station for everyday users and gamers.
    Reply
  • Llamaking2
    The article states:
    Unfortunately, Jarrod neglected to share details on the external GPU dock he is using, only noting that it's a Thunderbolt 3 dock -- which is good considering most GPU docks today are using Thunderbolt 3.

    Although in the video embedded states pretty clearly at 0:14 it is a Razor Core X Chroma dock that he had to modify slightly to get the 4090 to fit inside of.
    Reply
  • tek-check
    DavidMV said:
    Did anyone expect anything else??? it is PCIe 3.0 x 4 vs PCIe 4.0 x 16. That is an eight times transfer rate difference. Thunderbolt 5 with PCIe 4.0 might stand a little bit better chance with double the transfer rate of Thunderbolt 3.
    Exactly. In addition, 4090 would perform better in desktop Gen3 x4 slot as Thunderbolt also has an overhead.
    Reply
  • NTR
    Unfortunately, Aaron Klotz can't even extrapolate information 20s into the video YIKES...
    Reply
  • escksu
    Not surprising. I would say it's definitely has to do with the resizable bar and thunderbolt bandwidth. Since tb 3.0 is essentially a pcie 3.0 4x slot, 4090 is definitely going to struggle on it, esp. if there is resizable bar enabled. TB has its own overhead so actually bandwidth is even lower than that of a pcie slot.
    Reply
  • Keng Yuan
    Asus should make their proprietary eGPU port a common standard
    Reply
  • Kamen Rider Blade
    Keng Yuan said:
    Asus should make their proprietary eGPU port a common standard
    Or we can get PCI-SIG to push the External OCuLink connector into mass production.

    Then we can all benefit from having External PCIe connector that we can all use.
    Reply
  • edzieba
    DavidMV said:
    Did anyone expect anything else??? it is PCIe 3.0 x 4 vs PCIe 4.0 x 16. That is an eight times transfer rate difference. Thunderbolt 5 with PCIe 4.0 might stand a little bit better chance with double the transfer rate of Thunderbolt 3.
    For performance numbers that bad, it's very clearly not the bandwidth at fault: https://www.techpowerup.com/review/nvidia-geforce-rtx-4090-pci-express-scaling/28.html (TB3's PCIe 3.0 4x link is effectively the same as a PCIe 1.0 16x link).
    From bandwidth limiting alone, only a reduction to 80% of stock PCIe 4.0 x16 performance would be expected. To see 50% or below indicates there is much more at play than merely bandwidth.
    Reply
  • 🤣🤣🤣😂😂😂

    junk. This is what you can expect from now on. With these ridiculous power requirements I don’t see things getting any better in the future.

    this card is so stupid. what’s the next version gonna be like 2 kW of power required?!?

    this has to be their worst design ever. The technology is moving backwards at this point.

    people should vote with $$. Just say no. Save yourself $2000!!!

    for that money, you can get a really nice designer dog. And the dog will love you, unlike this silly card.
    Reply
  • InvalidError
    The eGPU might perform better with an external monitor attached to it so output doesn't have to piggy back over TB.
    Reply