The Steam Deck does seem to suffer from a CPU bottleneck when you install a massive external GPU.

The Steam Deck is a remarkable device. It provides almost laptop-quantities of power for gaming on the go, allowing Steam users to play almost any game from their library no matter where they are.

However, the Deck is still limited by its hardware, and that means its performance doesn’t quite measure up to a true desktop gaming PC. But what if we could change the Deck’s hardware to match that of a gaming desktop?

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That’s the question posed by ETA Prime, a tech YouTuber who set out to bridge the game between a gaming desktop and the Deck. The biggest factor separating the two is graphics power, so ETA Prime decided the best solution was to connect an external graphics card.

This turned out to be easier said than done. To start, there’s no PCI-E slots in the Deck, and the only option ETA Prime had to even install an external GPU was to use the M.2 slot that normally houses the Deck’s internal storage drive. Using an M.2 adaptor and an external PCI-E dock, ETA Prime was able to connect a Radeon RX 6900 XT to the Deck.

It should be noted that only Radeon-branded video cards worked with the Deck. Every Nvidia card, from the lowly GTX 1650 to the mighty RTX 3080 just didn’t allow the Deck to boot Windows 11, which was stored on the microSD card.

So, how did the Deck do? ETA Prime admits that this exercise told us less about the Deck’s potential performance with an external graphics card and more about what games are optimized for CPU processing and which games are optimized for GPU processing.

"Of course, the CPU in the Steam Deck is going to bottleneck this card for sure," noted ETA Prime, "but I still want to see what it can do with a massive GPU attached to it."

The Witcher 3 was able to run at 4K, ultra settings, and maintained a solid 100 fps. GTA 5 similarly was able to play at 4K and very high settings at 73 fps. On newer games, however, the CPU bottleneck became apparent. Elden Ring and Cyberpunk 2077 were only able to output around 50 fps, while God of War at 4K and ultra settings was stuck in the low 40s. Even dropping the settings on these games didn't really improve performance all that much since the GPU wasn't the component being overworked.

The other problem with this setup is it removes the Steam Deck’s main selling point: its portability. It sort of turns your sleek little Deck into a mess of wires and fans. The future of the Deck is looking pretty bright though, so maybe a Deck update will allow it to run with a slightly smaller Nvidia card.

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Freelance writer and contributor at The Gamer, Sean hails from Toronto, Canada. If you ask Sean what he likes, he'll say, "Robots, Ninjas, donuts - in that order."