AMD GPUs may FINALLY have a legit HDMI 2.1 work around in Linux. Must read if you plan on building a SteamOS living room PC connected to a TV

JohnnyFootball

JohnnyFootball

GerAlt-Right. Ciriously.
If you have an nvidia GPU, you don't have this issue. You have other issues. Also, if this is on a desktop, it doesn't matter since AMD can just use display port.

Long story short, if you hook up a Linux PC with an AMD GPU using HDMI (like to an OLED TV) you are limited to only HDMI 2.0 speeds, meaning you can get 4K/120 BUT you are limited to 8-bit RGB at 420 instead of full 10-bit 444 at 144Hz. This is due to AMD drivers being open source on Linux and the HDMI Forum refusing to certify. Whether you agree or not. That is the situation. I blame the HDMI Forum and would love to see the Linux community file a lawsuit...but whatever.

To be fair..most people could run an AMD GPU using those bandwidth limitations and it would still look fine to most people. I, myself, didn't notice the degraded color until I was made aware of the limitations. Sadly, once I noticed it, I couldn't unnotice it...:-(

Workarounds people tried, were DP to HDMI cables that required custom firmware that would sometimes work, but often lost HDR, VRR and/or both. It just wasnt stable or reliable.

However, it appears that UGREEN, who gets advertised on a lot of youtube tech channels might finally have the perfect cable.



I know we're gonna get the "fuck linux" "fuck amd" users coming into this thread to assure us that windows will rule the rest of our lives and that nvidia will always be the winners...please just fuck off and be grateful that other options are out there. Linux still is not the perfect gaming setup, but it is in a state where most newcomers can use it just fine. I've installed it for several novice pc gamers and they love the ease and simplicity.

If this ends up being a legit cable that can get 144 Hz (the LG OLED C4 and higher supports 144Hz) on an AMD GPU with no bandwidth, I will sell my 5070 Ti, buy a 9070XT and install Bazzite on my living room PC.

I felt that this was worth sharing. The HDMI 2.1 can legit become an achilles heal for AMD and that issue needs to get resolved as nvidia is not that far off from having a viable living room Linux experience.

I have no idea when this will be available in the US, but this is absolutely something that needs to be kept an eye on.
 
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Poppinfresh said:
Great news for people thinking about getting a SteamBox, because this issue would have almost certainly impacted them.
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Still. Getting the issue resolved with the HDMI forums is far and away the most desirable option.

It still requires quite a bit of tweaking and user work to get it to work properly, but in time it will hopefully become a non-issue.

I was using the Cablematters DP to HDMI 2.1 cable and it I was able to get it work, I was not able to keep it working though and I got tired of having to fickle with it over and over.

AMD really needs to get in gear and find some sort of workaround.

The biggest leg up AMD has on nvidia is linux performance. nvidia is slowly starting to take this issue seriously, which is a VERY good thing for those of us fed up with Windows.
 
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You can't install Steam OS on anything other than a Steam Deck or presumably the upcoming GabeCube

If you were building a loving room gaming PC and wanted to install some flavor of Linux out of the thousands of variants out there it might be Bazzite or something but it won't be Steam OS
 
Unknown Soldier said:
You can't install Steam OS on anything other than a Steam Deck or presumably the upcoming GabeCube

If you were building a loving room gaming PC and wanted to install some flavor of Linux out of the thousands of variants out there it might be Bazzite or something but it won't be Steam OS
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You actually can, but Bazzite is an infinitely better option.
 
JohnnyFootball said:
The biggest leg up AMD has on nvidia is linux performance. nvidia is slowly starting to take this issue seriously, which is a VERY good thing for those of us fed up with Windows.
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I use Nvidia with Linux and it's almost flawless at this point. I don't even notice a performance difference. Granted, I have a 5090 so I may be brute-forcing myself through it, but I can't see switching to a AMD card, unless they offer something in the high-end space, akin to the xx90 series from Nvidia
 
Poppinfresh said:
I use Nvidia with Linux and it's almost flawless at this point. I don't even notice a performance difference. Granted, I have a 5090 so I may be brute-forcing myself through it, but I can't see switching to a AMD card, unless they offer something in the high-end space, akin to the xx90 series from Nvidia
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Im getting there with my desktop PC with my 4090.

Getting there...but I am going to wait until DX12-to-Vulkan can offer comparable performance to windows.
 
Outside of this issue thats now fixed, HDMI 2.0 does not allow 4K@120hz, even when a lower colour bit depth and chroma subsampling is used its limited to 18Gbps, which allows 4K@60hz max.

I saw someone write this in another thread and was confused there, if you're getting 4K@120hz out of the card then the bandwidth of the port/cable must have exceeded 18Gbps.
 
Kuranghi said:
Outside of this issue thats now fixed, HDMI 2.0 does not allow 4K@120hz, even when a lower colour bit depth and chroma subsampling is used its limited to 18Gbps, which allows 4K@60hz max.

I saw someone write this in another thread and was confused there, if you're getting 4K@120hz out of the card then the bandwidth of the port/cable must have exceeded 18Gbps.
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No, you can get 8-bit 420 4K/120 in Linux. That is right around 18 GBps.

Believe it or not, 8-bit RGB 420 doesn't look too bad and most people wouldn't notice unless they know what to look for.

Video Bandwidth Calculator - Chen Index

My personal website providing software and resources for learning and reference purposes only.
trychen.com trychen.com
 
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Nice! That's awesome to hear from AMD folks, as I know the conversion cables could be hit and a miss on certain setups. Seeing that reddit thread show a video of the person getting HDMI CEC support to work, holding the xbox button down, and both booting the computer from sleep +turning on the TV was a flex.

It's annoying this even needs to be done though, and displayport should've always been the TV port standard because the HDMI forum license fees are among the worst in connectors.

Another bonus for me today was seeing Zen Browser add support for fractional scaling in Wayland on Linux.
 
That's the crazy thing about protocols these days. You can do everything correctly, but than some kind of copy protection (this is nothing else, not certified = you're out) comes into your way and cripples your good work.

Is there any reason why HDMI is still in use instead of display port? Only backwards compatibility as far as I know. And this can be achieved via adapters. Or can HDMI do something DP can't?
 
I don't even have a 4K TV, let alone a 120hz HDR one, but I'm oddly still tempted. Maybe it's FOMO or fearing a future price hike because this is currently the one solution. So far I've found Ugreen stuff to be solid.
 
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