External Thunderbolt Graphics Card Enclosures – Turn on “Beast Mode"

Michael Fiechter

26 September 2017


Thunderbolt 3 has brought a myriad of new connectivity options to the computing world. Using USB Type C as a connector, Thunderbolt 3 offers 40 Gbit/s of low latency bandwidth between external devices and your laptop. Additionally, it can transport up to 100W of power, so you only need a single cable for most applications. Thunderbolt 3 docking stations, for example, allow you to connect multiple high-resolution displays, fast external storage, a network link, and a power supply over one single connection.

Since the bandwidth is so high, it opens up the door to a previously unfeasible idea: connecting a full-size desktop graphics card to a laptop. External graphic card enclosures (eGPU) like the HP Omen Accelerator allow you to attach any current desktop GPU, starting with the AMD R9 series and the Nvidia GTX 9 series to any laptop with a Thunderbolt 3 connection. The Omen also offers a slot for a 2.5” hard drive or SSD, 4 USB-A and 1 USB-C port, and a RJ45 Gbit-Ethernet port. All eGPU docks expose the monitor connectors of the graphics card that’s installed, so you can attach external displays directly to it.

Using an eGPU

Before you can use an eGPU, you’ll have to install a graphics card into the device. Current and last generation GPUs will mostly work, but it’s always a good idea to check for compatibility on the manufacturer’s page first. Our tests with an Nvidia Geforce GTX 1060 and a 1070, as well as a AMD Radeon RX 480 went fine. Afterwards, you can connect the eGPU to your Thunderbolt 3 port for the first time. The Thunderbolt security system will prompt you to confirm the connection and Windows 10 will automatically install all the drivers you need to run the box. This can take quite a while, since large amounts of data will have to be downloaded and installed. One or two reboots are also necessary to make everything work smoothly. For any laptop requiring less than 100W, charging should also happen over Thunderbolt 3. More power-hungry laptops like workstations will still need an additional power supply.
Once everything is set up, you can start using your new external computing power. Just like on laptops with a dedicated graphics card, the system should automatically switch between the GPU on your CPU and your eGPU. More often than not, however, you’ll first have to run a program once, only to tell the graphics driver afterwards that it should use the eGPU, since automatic detection doesn’t seem to run perfectly yet. Both the Nvidia and the AMD driver feature extensive options where you can the system how the eGPU and any attached displays should behave.

If everything is running smoothly, you can expect similar performance from your graphics card in the external box as you would expect in a full-size desktop system. With the Unigine Superposition benchmark, for example, we got similar results for the GTX 1060 in a desktop system with an Intel Core i5-2500K with 16GB of RAM as with the same GPU in a box attached to our HP x360 1030 G2 (2204 vs. 2169). We also tested games and GPU compute applications like crypto mining, and the performance boost over internal GPUs is huge . You can use your ultrabook that only sports an onboard Intel GPU for gaming in AAA titles or you can multiply the power of your workstation for anything from CAD to machine learning.

Limiting factors

In general, the manufacturers claim, and our measurements confirm, that you’ll have to expect a performance hit of 5-20% when running the GPU externally, depending on the graphics card and the application. With eGPUs, there are two factors limiting performance: The Thunderbolt connection and the CPU in your laptop. The 40 Gbit/s of bandwidth offered by Thunderbolt 3 still only represent a PCIe 4x connection. In desktop machines, however, GPU are usually attached over PCIe 16x connections, giving you 4x the theoretical bandwidth. For any applications that rely on constant communication between the CPU and the GPU, like gaming, this can represent a bottleneck. Similarly, if your CPU can’t keep up the graphics card, which can happen in applications where both processors share the load like in gaming or media creation, you also won’t be able to use the full potential of the graphics card. However, for crypto mining or many GPU compute applications, the speed of your connection or CPU are mostly irrelevant. For those applications, data is loaded onto the GPU fairly infrequently and the GPU will work for quite a while (at least in computer terms) until results are sent back to the system.

Conclusion

For many applications, an eGPU can both replace a docking station and a full-size desktop PC. However, you’ll need to do some research on which GPU will be most suitable for your need and you need to know how to fix some inconveniences with the graphics driver. Laptops that already have a dedicated GPU are particularly prone to problems in deciding on one of the three available GPUs when you attach an eGPU. Choosing the right graphics card, on the other hand, is not that difficult: for anything that is constrained either by your CPU or by Thunderbolt 3, it doesn’t make much sense to go above mid-range GPUs (AMD RX 580 or Nvidia Geforce GTX 1060). For anything else, you can go as high as you like, as most external boxes like the Omen Accelerator can support any GPU up to 300W. Feel free to contact us at kontakt@projektneptun.ch if you have any questions. You can find the HP Omen Accelerator in our shop under "HP Peripherie & Diverses".