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Valve is not concerned about the limited VRAM on its upcoming Steam Machines, but maybe it should be. New testing from Ars Technica suggests that Windows 11 performs significantly better with 8GB of VRAM than SteamOS, particularly with certain games and settings.
Until recently, only the most high-end GPUs topped 8GB of VRAM; the RTX 3080 shipped with just 10GB in 2020. However, many games now demand more than that for even recommended settings, meaning gamers with limited VRAM end up with low settings and resolutions.
Valve claims that this shouldn't be an issue with the Steam Machine's APU, but testing suggests otherwise. In its benchmarks, Ars found that games like Returnal are playable on an RX 7600 with just 8GB of RAM at 1440p and max settings in Windows. But switch to SteamOS, and the performance is less than a third. The same issue is not present with the 16GB RX 7600 XT.
Cyberpunk plays slightly worse on SteamOS with ray tracing disabled, and significantly worse when enabled. Even the older Assassin's Creed Valhalla at 1080p max settings was around 15% weaker on SteamOS when limited to 8GB of VRAM.
It's not a significant issue in every game, and ray tracing -- a setting that few are likely to enable on weaker hardware -- appears to be the primary reason for 8GB of VRAM performance degradation. However, the dip is also present in games with less demanding graphical options.
In the desktop testing scenarios that Ars put together, the Windows systems performed slightly better across the board in every game they tried. That's the inverse of what we've seen on a lot of Windows handhelds, where SteamOS appeared to play better with the APU. It may be that on Steam Machines (with a similar APU versus the CPU and GPU combo Ars used), we'll see better SteamOS performance in limited VRAM scenarios.
Still, it does seem to suggest that 8GB of VRAM can be a severely limiting factor for performance in certain SteamOS settings and games. Valve will need to continue tweaking that if it wants to claim that its new gaming platform -- which could cost close to $1,000 if RAM shortages continue -- is worth it over game consoles and similarly specced standard desktops.