When the valve announced its new Steam Machine hardware last monthsome eagle-eyed gamers may have been surprised to see this official specification Specifies support for HDMI 2.0 output rather than the updated, higher-bandwidth HDMI 2.1 standard. introduced in 2017. Valve now tells Ars that while the hardware itself does in fact support HDMI 2.1, the company struggles to offer full support for the standard due to Linux drivers that are “still being worked on in software.”
How we celebrated last yearThe HDMI Forum (which manages the official HDMI standards specifications) has officially blocked any open source implementation of HDMI 2.1. This means that the open source AMD drivers used by SteamOS cannot fully implement certain features specific to the updated output standard.
“Currently, an open source implementation of HDMI 2.1 is not possible without violating the HDMI Forum requirements,” AMD engineer Alex Deutscher said at the time.
They do what they can
This situation caused major problems for Valve, which tells Ars that during testing it had to check the Steam Machine's HDMI 2.1 hardware through Windows. And regarding HDMI performance over SteamOS, a Valve spokesperson told Ars that “we're working on trying to unlock some things.”
This includes unlocking HDMI 2.0 resolution and frame rate limitations, which maximum frequency 60Hz for 4K outputaccording to the official standard. Valve tells Ars that they were able to increase this limit to the “4K at 120Hz” specified in the Steam Machine specifications, thanks to technology called chroma subsampling.
