Why won’t Steam Machine support HDMI 2.1? Digging in on the display standard drama.

In a recent reveal of its Steam Machine hardware, Valve has caught the attention of gamers by specifying HDMI 2.0 output support instead of the more advanced HDMI 2.1, which was introduced back in 2017. This decision has raised eyebrows, prompting Valve to clarify the situation in a conversation with Ars Technica. Despite the hardware being capable of supporting HDMI 2.1, Valve explained that the company is currently facing hurdles in providing comprehensive support for this standard. The issue largely stems from ongoing work on Linux drivers, which are not yet fully developed. The HDMI Forum, which oversees the official HDMI specifications, has prohibited any open-source implementation of HDMI 2.1. Consequently, the open-source AMD drivers utilized by SteamOS cannot fully adopt certain features inherent to the new standard. AMD engineer Alex Deucher noted the challenges, stating, "At this time, an open-source HDMI 2.1 implementation is not feasible without violating the HDMI Forum's requirements." This predicament has led to considerable difficulties for Valve, which has had to conduct validation of the Steam Machine’s HDMI 2.1 hardware using Windows during its testing phase. Regarding HDMI performance on SteamOS, a Valve representative indicated that efforts are underway to resolve existing limitations. These include addressing HDMI 2.0's restrictions on resolution and frame rates, which are capped at 60 Hz for 4K output. However, Valve has managed to enhance this limit to “4K @ 120Hz” as noted in the Steam Machine specifications, utilizing a technique known as chroma sub-sampling.