The TL;DR is that the organization that controls the HDMI standard won’t allow any open source implementation of HDMI 2.1.
So the hardware is fully capable of it, but they’ll get in trouble if them officially implement it.
Instead it’s officially HDMI 2 (which maxes out at 4k @ 60Hz), but through a technique called chroma sub-sampling they’ve been able to raise that up to 4k @ 120Hz.
However there are some minor reductions in picture quality because of this, and the whole thing would be much easier if the HDMI forum would be more consumer friendly.
In the meantime, the Steam Machine also has display port as a completely issue free display option.
The communication protocols are just different enough that an adapter won’t work.
The adapters have circuity inside, they exist. It’s small enough to still just look like a cable because they fit the chip in a plug end.
Til
DP has an option to transmit HDMI signals instead, this is what passive adapters use and will still have the same HDMI 2.0 issue. A DP source can be passively adapted to HDMI, but a HDMI source cannot be passively adapted to DP.
You can also get active HDMI adapters which actively convert the signal, and can work with HDMI 2.1. Intel actually has an active converter chip built into their ARC GPUs, and is how they get around this issue.
What a bummer. I guess TIL that i, in fact, don’t use one literally every single day.
Is it 2.1? Does it transmit cec commands? No? Strange…
It’s almost like we are commenting under a post that is saying exactly that.