Like all portable gaming devices, the Steam Deck sacrifices powerful hardware and a high-resolution display in favor of portability and battery life. As a result, you cannot run many games with high graphics settings, and some games do not work at all. ETA PRIME, a tech YouTube channel, decided to see whether it is possible to equip the Steam Deck with something more impressive than the stock APU from AMD. As it turned out, you can connect an external GPU to the Steam Deck and get a massive performance boost despite numerous constraints.
Of course, connecting an external graphics card to the Steam Deck defeats the device's purpose because a discrete GPU requires external power and cannot work from the built-in battery. Still, it is pretty interesting to see how the Steam Deck handles such an extreme task with no Thunderbolt or full-size PCIe ports.
To make the Steam Deck work with an external GPU — the RX 6900 XT in this case — ETA PRIME used an M2 to PCIe adapter and a standard off-shelf 750W PSU. Because the console has a single M2 port for its storage, the enthusiasts had to install Windows 11 on the Steam Deck using a microSD card (you cannot install the Steam OS on a microSD). Games, on the other hand, were running from an external SSD connected via USB-C.
Using an M2 to PCIe adapter significantly crippled the graphics card's performance due to the lack of enough PCIe lanes, but the GPU still could provide a massive performance boost. The video shows the Steam Deck running demanding games on high settings at the 4K resolution with respective frame rates. The Witcher 3, for example, runs at 100+ FPS at 4K with maxed settings. Also, the Time Spy and Fire Strike benchmark revealed up to a 5x graphics performance increase.
More modern games, though, despite working at high graphics settings, could not provide even 60 FPS due to CPU limitations. The God of War, Elden Ring, and Cyberpunk 2077 run at around 45-50 FPS regardless of the screen resolution or graphics settings, which is the ultimate sign of the CPU being too weak for the GPU. Still, it is worth mentioning that the stock Steam Deck cannot run these games at all.
It is hard to imagine anyone bolting in an external graphics card and a big PSU to the Steam Deck, but as the author claims, this experiment is not about usability and practicality. Instead, it is all about a proof-of-concept and "just because we can."