Radeon RX 9070 XT works as an eGPU on Valve Steam Machine
© Large_Customer_3840 A Steam Machine owner has connected a Radeon RX 9070 XT to Valve’s system using its i nternal M.2 slot. The modification effectively turns the compact PC into an eGPU-capable system, although it requires moving the original SSD outside the chassis.
Reddit user Large_Customer_3840 used an M.2 to OCuLink adapter connected to an AOOSTAR EG01 external GPU dock. The dock houses the Radeon RX 9070 XT and requires a separate desktop power supply. Since the Steam Machine only has one M.2 slot, using it for OCuLink means the internal NVMe SSD has nowhere to go.
SteamOS boots from USB-C instead
The user solved the storage problem by placing the Steam Machine’s NVMe drive inside a USB-C enclosure. SteamOS then boots from the external SSD while the internal PCIe connection is dedicated to the graphics card.
More interestingly, SteamOS required no manual GPU configuration. According to the modder, the Radeon RX 9070 XT immediately became the primary graphics adapter after the system was powered on. The display output worked without manually selecting between the internal and external GPUs.
The first gaming test was limited to Crimson Desert. The user reports more than 100 FPS using the High preset, although they only tested the configuration for about a minute. There is therefore no longer-term performance data or proper comparison with the Steam Machine’s integrated Radeon GPU yet.
A possible permanent Steam Machine GPU upgrade
The current setup requires the Steam Machine to remain open because the OCuLink cable has no dedicated route through the chassis. The owner says a modified case or backplate could turn it into a permanent upgrade. OCuLink itself uses four PCIe lanes, so an RX 9070 XT will not have the same bandwidth available as it would in a normal PCIe x16 desktop slot.
This is not exactly a clean upgrade path, since it requires an external SSD, GPU dock, desktop graphics card and separate PSU. It does show that SteamOS can recognize a much faster external Radeon GPU without additional configuration, and that the Steam Machine’s M.2 connection can be repurposed for OCuLink.
If only Steam Machine had USB-C with Thunderbolt 3/4 or at least a secondary M.2 slot, such mods would probably be a lot more popular. However this also shows that Steam Machine may not be limited to one GPU performance tier. The RX 9070 XT is much faster than Machine’s built-in RDNA3 GPU.
Source: Reddit
