Clever Mod Adds AMD GPU to Steam Deck for 4K Gaming

steam bridge

Valve has repeatedly insisted that the Steam Deck does not come with external GPU support, dashing gamers’ hopes of hooking up an RTX 3090 and throwing the graphics settings on Ultra. At the same time, Valve continues to emphasize that the Steam Deck is an open platform, a device that can be modified to suit a user’s needs and preferences.

So what does a handyman do with this information? Listen to what they wanted to hear and ignore the rest, of course. The people who run the ETA Prime YouTube Channel found a way to augment the Steam Deck’s AMD Zen 2 processor and custom RDNA 2 graphics with an AMD Radeon RX 6900 XT GPU, a high-end desktop graphics card.

It wasn’t easy, and you shouldn’t try this with your shiny new portable console, but the hack most work. ETA Prime originally wanted to modify the Steam Deck with an Nvidia GeForce GTX 1650 card, but they discovered that the Steam Deck didn’t play well with cards from AMD’s rival.

Since the Steam Deck doesn’t contain a Thunderbolt port (it uses standard USB-C), ETA Prime had to cobble together an M.2 connector with a PCIe x4 interface by replacing the internal SSD with an external dock. They then hooked up a desktop power cube to the GPU to give it the juice the little Steam Deck lacks. As you can imagine, the setup looks silly – you have a Nintendo Switch-like handheld daisy-chained to a massive GPU and chonky power supply. It’s not the kind of thing you could play on the train on your commute.

Since the M.2 slot was used for the external GPU, a microSD card had to be used for all operating systems and game storage. And while ETA Prime would have kept SteamOS 3.0 on deck, since Valve’s operating system can’t be booted from a microSD card yet, the mod uses Windows 11 instead.

After booting into Windows, ETA Prime opened Task Manager and discovered that with the native AMD APU the system was running on a Radeon RX 6900 XT external graphics card. It worked! Of course, hooking up a full desktop GPU to a handheld console is like putting a turbocharged V8 engine in a Ford Pinto – the other components weren’t designed to accommodate such a powerful card, so bottlenecks are inevitable.

And yet, even with a stunted RX 6900 XT, the Steam Deck quadrupled its performance in 3DMark synthetic benchmarks and played demanding games like The Witcher 3 at 4K resolution on Ultra settings at an average of 108 frames per second. Modified Steam Deck even played GTA V at 4K on Super High at 73 fps and Ring of Elden on 1080p at Max setting at 46 fps. Again, the Steam Deck’s RX 6900 XT card was bottlenecked by its low power consumption APU and slow storage, but even then the system saw huge performance gains.

This is obviously not the sort of thing you should try with your own system. The Steam Deck wasn’t designed to support external graphics cards, and adding one essentially turns this sleek portable console into a messy (but delicious) stationary desktop. Even ETA Prime warns against using this method to harden Valve’s console. So why did they do it? For the best reason: “Because we can”.

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