Steam Machine eGPU Upgrade: Testing an RX 9070 XT Over Oculink

Introduction

The Steam Machine is a compact gaming console with a semicustom AMD processor and a built-in discrete GPU. It has no PCIe slot and no USB 4 port, which normally rules out an external graphics card upgrade. But there is one path: the M.2 slot inside the machine. By connecting an Oculink eGPU dock to that M.2 slot, we were able to run an ASRock Tai Chi RX 9070 XT and roughly triple the frame rate in several games.

This setup is not something most people should rush out and build. It requires opening the console, occupying the only M.2 slot, and running the operating system from an external SSD. Still, the results show what the hardware is capable of when given more graphics power.

How the Setup Works

The Steam Machine normally houses a 2230 M.2 SSD in its single M.2 slot. In this build, that SSD was replaced with an Oculink to M.2 adapter. The adapter provides an X4 Gen 4 connection, which delivers around 64 gigabits per second through the cable. That is considerably faster than Thunderbolt 4, though Thunderbolt 5 and USB 4 V2 are catching up.

Because the M.2 slot was occupied, Steam OS had to run from an external drive. A 1TB SSD was cloned from the original internal drive and connected over USB. The Oculink cable was routed out of the back of the console, keeping the case closed during testing.

One important detail: all video output must come from the HDMI port on the external GPU, not the HDMI port on the Steam Machine itself. Routing everything through the external GPU ensures the RX 9070 XT handles all rendering work.

The Hardware: ASRock Tai Chi RX 9070 XT and Aostar AG03 Dock

The GPU used in this test is the ASRock Tai Chi RX 9070 XT. It is a large, premium card with a triple-fan design and 16GB of VRAM. It was not purchased specifically for this project, but it delivered strong performance in the games tested.

The dock is the Aostar AG03 eGPU dock. It includes an 800W power supply and three 8-pin PCIe power connectors, so it can handle high-end cards. The dock supports Oculink as well as Thunderbolt 3, Thunderbolt 4, and Thunderbolt 5 connections. It is rated to handle cards up to an RTX 5090, though this build used a Radeon card because Steam OS works best with AMD graphics.

The Steam Machine itself kept its six-core, 12-thread semicustom Ryzen CPU, which boosts up to 4.86 GHz. The system memory was upgraded to 64GB. That CPU is the main bottleneck in this setup, and it limits how much performance the RX 9070 XT can deliver.

Performance Testing: Native Resolution Benchmarks

In-game benchmarks were run at 1080p, 1440p, and 4K, all at native resolutions with no upscaling. The highest available settings were used in each game. Results were compared between the stock Steam Machine and the Steam Machine with the RX 9070 XT connected over Oculink.

In Shadow of the Tomb Raider, the stock machine averaged 118 FPS at 1080p. With the eGPU connected, that jumped to 168 FPS, about 42% faster. At 1440p, the stock machine hit 86 FPS while the eGPU setup reached 132 FPS, roughly 53% faster. At 4K, the stock machine managed 44 FPS, while the eGPU setup averaged 73 FPS, an improvement of about 66%.

Cyberpunk 2077 on the ultra preset with no FSR showed similar gains. At 1080p, the stock machine averaged 74 FPS, rising to 125 FPS with the eGPU. At 1440p, the stock machine hit 45 FPS, while the eGPU setup reached 71 FPS, about 58% faster. At 4K, the stock machine only managed 18 FPS, but the eGPU setup reached 51 FPS, a 183% improvement.

Horizon Zero Dawn Remastered on the very high preset proved to be heavily CPU-bound. At 1080p, the stock machine averaged 58 FPS, rising to 94 FPS with the eGPU. At 1440p, the stock machine hit 48 FPS, while the eGPU setup reached 81 FPS. At 4K, the stock machine averaged 26 FPS, and the eGPU setup reached 52 FPS, a 100% uplift.

These results show that the RX 9070 XT delivers substantial gains even when limited by the Oculink connection and the console’s modest CPU. The biggest improvements appeared at higher resolutions, where the extra GPU power matters most.

Real-World Gaming Experience

Beyond the synthetic benchmarks, several games were tested at 1440p with high settings. Cyberpunk 2077 at 1440p high with no FSR showed some dips, but adding FSR 2.1 at quality mode pushed the frame rate higher. With FSR frame generation enabled at native 1440p ultra, the average frame rate climbed above 100 FPS.

Ratchet and Clank: Rift Apart at 1440p very high with no FSR ran above 130 FPS consistently. This game struggles on the Steam Machine’s built-in GPU, which requires medium settings and FSR to balance just to stay above 60 FPS. Forza Horizon 6 at 1440p ultra with no FSR averaged in the mid-90s, a strong result at native resolution.

One issue appeared in Ratchet and Clank: the game initially tried to use both the built-in GPU and the external GPU at the same time, which caused frame rates to drop to around 16 FPS. This was fixed by forcing the game to use the RX 9070 XT through the game’s properties settings.

Things to Consider Before Trying This

This is not a straightforward upgrade. The Oculink cable used in this build was finicky and not very durable, and the first cable did not work correctly. The M.2 slot is the only one in the machine, so the operating system must run from an external SSD. The CPU is also a limiting factor, as it sits around 3.2 GHz during gaming despite a 4.8 GHz boost rating, due to its 30-watt TDP.

There were occasional audio crackling issues in menus, likely related to ASPM power management over the PCIe lane. Disabling ASPM did not improve performance, so it was left enabled. The setup also requires opening the console and routing a cable out of the case, which is not practical for most users.

For those who want a more powerful Steam Machine, a USB 4 port would have made this much easier. Unfortunately, the console does not have one. This build works, but it is a project for enthusiasts rather than a recommended purchase path.

Buying Advice

If you already own a Steam Machine and want to experiment with an external GPU, the Aostar AG03 dock is a capable choice. It provides plenty of power, supports multiple connection standards, and can handle high-end cards. The ASRock Tai Chi RX 9070 XT is a strong performer, though it is a premium card that costs more than the console itself.

For most people, the better path is to wait for a console or handheld with USB 4 support, which would make external GPU connections much simpler. But for those who enjoy tinkering and already have the hardware, this setup delivers real performance gains, especially at 1440p and 4K.

Conclusion

Connecting an RX 9070 XT to a Steam Machine over Oculink is a niche project, but it works. The performance gains are significant, with frame rates nearly tripling in some titles. The main limitations are the CPU, the single M.2 slot, and the finicky nature of Oculink cables. If you are comfortable with the trade-offs, this is a fun way to breathe new life into the console. Otherwise, it is best left as an experiment for enthusiasts.