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Comment by max-leo | Hacker News Reader

> HDMI 2.0

The HDMI Forum yet again rearing it's ugly head by continuing to block GPU manufacturers from implementing HDMI 2.1 in the Open Source drivers

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Yup. This really needs to be fixed. There have been on-going bug reports on it for years. AMD just needs to move the hdmi 2.1 stuff behind a firmware binary blob already like NVIDIA does. It's so annoying not having full quality HDMI. It's the only think keeping me from using Linux on my current gaming PC that is hooked exclusively up to my TV... Either that or TV's need to start having Display Port.

This is a big miss for me. I can’t use my TVs 120Hz VRR mode without HDMI 2.1.

I realize the Xbox Series X is beleaguered at this point, but apart from playing games that are on Steam but not Xbox, I can’t see why I would prefer the Steam Machine.

After commenting i looked up the actual capabilities of the port and it turns out while the port is officially only HDMI 2.0 it actually still supports 120Hz, HDR and VRR anyway. So basically it only doesn't support Display Stream Compression for 144Hz and beyond.

I quickly tested this by connecting my PC running Linux with a RX 6800 to my TV (LG C4). 120Hz, VRR and HDR were all available.

At 4K? Or are you limited to a lower resolution due to bandwidth constraints?

Try for yourself. I get 4k120Hz when connecting my laptop directly via HDMI.

Yeah I have tried it for myself. I am limited to 4K60 when using the HDMI 2.0 port on either my M1 Mac mini or M1 Pro MacBook Pro and LG B2 TV. I do get 4K120 with VRR with newer Macs with HDMI 2.1 as well as my Xbox Series X. It has been my understanding that 4K120 with HDR and VRR requires HDMI 2.1, which is why those HDMI 2.0 limited systems don’t work. Not having a Steam Machine myself, I would assume its HDMI 2.0 port would be similarly limited.

Edit: I should add, I do get 4K120 VRR and HDR on the M1 Macs when connected to a monitor via Thunderbolt or Thunderbolt to DisplayPort adapter, and I would expect a Steam Machine to be similar using DisplayPort, but my TV only has HDMI input and so can’t work in this mode (and a Thunderbolt to HDMI adapter doesn’t work either).

I get 4k120Hz when connecting the output from a HDMI 2.0 port on my laptop to the HDMI 2.1 port on my TV (Sony TV, it has 4 HDMI ports, but for some reason only ports 3 and 4 support HDMI 2.1, 120Hz, VRR).

Yes, 4K120Hz! My TV could do 144Hz but i couldn't select it so 4K120 seems to be the limit.

"Luckily," the hardware won't allow for 4k@120Hz on visually cutting edge games anyway.

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