Would GPU passthrough for use with a CRT tv be possible on linux?

kakuyamii · Yesterday 02:56:18

I'm planning on making a little convoluted setup so I can play games on a CRT tv that I plan on buying, or watch movies and stuff like that.
The idea is to have one gpu (RX7600) render all the graphics and the game itself so all the workload is on that, and all the frames should be sent to the second gpu (Radeon R9 285) that supports analog input and interlaced (such as 480i and above) resolutions only shows the frames being rendered.
The analog input would be necessary for the crt tv OR crt monitor to show the frames without rendering them so that the game or anything else runs smoothly, though I'm not quite sure if this would be possible on linux or not...The only documented example of GPU passthrough i've seen being used in this way was on this video:
https://www.youtube.com/watch?v=puu-iyTsZtg
Which, not only used nvidia gpu's (Not what I have, wouldn't be using amdgpu drivers and nvidia support is sorta finnicky..?) but used a very specific and *barely* documented feature on windows..11. which in no way in hell I wanna use.
I'm not sure if this sorta method would be possible on x11 or wayland or on linux in general, but i figured this would be the place to give it a shot and try to ask if it is because i doubt any crt tv forum or reddit would have much help since most people doing that sorta setup are windows users anyway.
if anyone is able to help with this, i'll be VERY thankful and will try it out when i'm able to!!

cryptearth · Yesterday 06:04:48

i might be wrong - but a Rn 200 doesn't support analog output
in fact the last "radeon" card that still supported analog outout was still branded ATI - when amd changed the branding it already was all digital
so you would need a much older card - but then you likely run into the problem that such an old card doesn't work in a modern platform anymore which you require to run your modern rx7000
these worlds are just too far apart it seems

aside from that: "out of the box" - no, render on one gpu and use a second as output device to convert outout signals - i doubt that would work - at least not without additional specialized software and maybe even drivers

i think i can guess where this going - but honestly: if you want retro - just build a retro system as its own second machine - try not to fall into a XY trap here

Last edited by cryptearth (Yesterday 06:05:09)

seth · Yesterday 08:07:20

i might be wrong - but a Rn 200 doesn't support analog output

Why not?
It needs to have a VGA or DVI-I output, or you'll need an active adapter.

As for the output redirection: on X11 check "xrandr --listproviders" and post your X11 log.
If it works on X11 it can *theoretically* also work on random wayland compositors. Whether it does (and how complicated it would be to configure) depends on the compositor.
But in general https://wiki.archlinux.org/title/PRIME (or reverse prime) is not limited to nvidia at all

You can test the latter completely w/o a CRT, just attach whatever you have to the R9 and make it display stuff rendered on the RX7600

Succulent of your garden · Yesterday 10:00:07

In theory with the VGA or DVI-I adapter for gpus that only send digital signal, it's possible. As far as I know gpu now days are able to render 800x600 resolution, so with a good digital-analog adapter you should. I mean there are people that uses nvidia + amd gpu to render and show fps in new games now day, so it's mostly probably that you can with your stack.

I checked now your gpus and your older one have two DVI-I connectors, so in that case maybe it's not necessary to use the digital-analog adapter. You can install both drivers since both cards are amd [You can't have two different nvidia series in some cases], so the main issue would be that they 7600 can't send the data to the grandpa card by pci lanes.

Also It seems you can upscale your old games with this https://wiki.archlinux.org/title/Gamescope . Remember that crt monitors emits low levels of radiation but that in the "latest" versions were handle well for human usage. But if you want to omit the radiation thing, then maybe upscaling your old games can be a thing. I think there are more upscalers also around, but I know it's a thing. Also this exits and is in steam as the wiki says: https://en.wikipedia.org/wiki/RetroArch

Last edited by Succulent of your garden (Yesterday 11:44:13)

kakuyamii · Yesterday 10:37:06

i did some research based on what you guys said and managed to find this handy guide while on the hunt for out of the box stuff:
https://silosneeded.com/2025/11/pc_crt_guide
i checked the batocera crt script wiki, and...my rx7600 CAN generate interlaced video actually!! though, it'd be a bit of a specific setup to get it working, but seemingly cheaper than having to set up the other setup involving the grandpa gpu card.
it'd be essentially:
connecting the component input to a vga converter (which keeps it analog at least, so no downscaling presumably?) then to a displayport input to be plugged on the GPU's displayport output since they *are* capable of displaying interlaced input and lower resolutions like 240p/240i with superresolutions or just regular resolutions, but that would also require me to install groovyarcade which...to me isnt really an issue HONESTLY
retroarch has enough emulators i need, and even then i could probably try out batocera? i'd probably be able to dual boot with batocera on the side of my main distro to set it up, and i think that would have less input lag than doing passthrough with prime

cryptearth · Yesterday 10:56:31

neither the RX7000 nor the Rn 200 series have anslog capable DVI-I connectors
in fact tge Rn 200 series only have digital only DVI-D connectors and the RX 7000 don't have any DVI anymore but only DisplayPort and HDMI

so no matter how - if OP requires an analog outout tgey need an active converter - or an even older card supporting a true analog DVI-I output

// edit F5

kakuyamii wrote:

rx7600 CAN generate interlaced video actually

well - yes ... because interlaced is still part of HDMI - but tgat's still a full digital signal
to hook up a CRT via VGA you need an analog signal - and THAT neither tge RX nor the R9 are able to generate

interlaced != analog

Last edited by cryptearth (Yesterday 11:00:19)

Succulent of your garden · Yesterday 12:06:59

Upscaling and playing with retroarch could be the fastest way to play your games, but if you want the nostalgia of the crt monitor then probably you have two options basically:

Buy a good digital-analog converter [which take some space, but not too much], you need the converter because there are sometimes some adapters that are small to hdmi to DVI-I signals, but that things doesn't work, you need some kind of box who makes the adaptation for signals.

Or use your Radeon R9 285 to send the fps to monitor and rendering with the RX 7600, which is a nice thing cuz amd let's you make that, imagine doing this with an 1000 series and 5000 with nvidia, you can't :C. With this you will not need the converter because your R9 285 can be able to send the analog signals, in that case if your monitor does only supports vga, you can buy an vga to DVI-I adapter and will work, back then I had an old pc and made that because I had the same issue as you. Monitor only with vga, and gpu only with DVI-I. tldr: Analog adapters for analog adapters will always work, there are small you will not notice it behind your computer because they hold in the gpu with the screws of DVI-I input interface.

The delay between gpus i think is gonna be really small, like maybe 3 or 5 milliseconds at most, or maybe even less. It's gonna depend from this factors:

1) Which pci version is your mobo ? If it is 5.0 RX7 7600 is pci 4 and uses x8 lanes, so you will have more than enough bandwidth to use the card 100% and also the grandpa gpu one. If you have pci 4.0 then but your mobo uses x16 lanes for one gpu and x8 x8 for two then you are more than enough to not complain about the pci transfer latancy. I mean even now days PS3 emulations in pc makes the games run faster with more fps than the original running in stock PS3, so I think is kinda an overkill to try to fix the latancy, in any case if you want to because it's fun or because I can, then probably you can reduce that by compiling everything in your machine, for that probably you will need something like gentoo or linux from scratch. But the main question is: Are you going to use this pc for something else ? because if it's your main pc then probably it's not a good idea if you want something that is stable always cuz you need to go into a meeting in zoom or whatever video call.

But it is only a gaming pc, then probably you should also check this: https://bazzite.gg/
I use it for gaming and it's good, but I had never used it for like playing old games, but it does have the support.
If you want something good and easy for maintain, then it's also an option. But if you want to keep it in Arch by some reason then it's fine, honestly I use bazzite cuz is easy to maintain and also provides me a decent option for playing my RTS games and don't makes conflict with my WM keybinds configuration

seth · Yesterday 14:37:56

neither the RX7000 nor the Rn 200 series have anslog capable DVI-I connectors

Source?
https://bbs.archlinux.org/viewtopic.php?id=251548

cryptearth · Yesterday 16:02:23

gcn3.0 tonga datasheet straight from amd.com (somehow can't link on phone - for link please wait until i'm home in a few hours)

seth · Yesterday 16:11:04

@kakuyamii what's the actual graphics card model (vendor/name, not the AMD chip but MSI, GigaByte etc.) ?

Succulent of your garden · Yesterday 16:20:18

seth wrote:

Source?

actors-john-cleese-and-terry-jones-in-the-mr-creosote-sketch-from-the-film-monty-pythons-the.jpg?s=612x612&w=0&k=20&c=11BlTIJV-lFeW8NzDJFSvde6nrqjwD5RB2PWSojtbMU=

Here you have monsieur:
https://www.techpowerup.com/reviewdb/Gr … D/RX-7600/
https://www.techpowerup.com/review/sapp … dual-x-oc/

I wasn't able to find the happy version in the home, before this :C
So i went with Mr Creosote :C.

https://www.techpowerup.com/review/sapp … dual-x-oc/

EDIT:

All rest of gpus manufactures:

amd-radeon-r9-285-features-1-792-stream-processors
img source: https://www.techpowerup.com/204462/amd- … processors

https://www.techpowerup.com/vgabios/176675/176675

https://www.techpowerup.com/gpu-specs/h … 2-oc.b3043

https://www.techpowerup.com/204505/asus … d-pictured

https://www.techpowerup.com/gpu-specs/x … tion.b3117

https://www.techpowerup.com/vgabios/176675/176675

the only that I had not found is the msi, but in the photo it seems it does have DVI-I or VGA.
All gpus have at least one analog connector.

Last edited by Succulent of your garden (Yesterday 16:27:21)

seth · Yesterday 19:20:39

crypthearth's claim was the the GCN 3.0 GPUs do NOT have analog CRTCs and while I find the generalization odd and https://bbs.archlinux.org/viewtopic.php?id=251548 suggests different, none of the links I clicked on also really disproofs that (just because there's a DVI and even DVI-I connector doesn't proof that there's an analog signal)

I guess it's best to hear what actual card we're dealing with and then investigate that.

Succulent of your garden · Yesterday 23:21:25

Oh forgive me god of death, infertility and destruction [seth is an Egyptian god, old inside joke] for I have sinned, Betrachte, meine Seel and please educate me on these:

seth wrote:

crypthearth's claim was the the GCN 3.0 GPUs do NOT have analog CRTCs

You mean CRTCs as equal to CRT monitors ? I'm understanding that GCN architecture is not supporting analog signals.

seth wrote:

just because there's a DVI and even DVI-I connector doesn't proof that there's an analog signal

Is this really possible ? like the manufacture added the DVI-I and the gpu architecture is not able to support frame display into the the analog socket ? Why it could be that a thing that was made in the past ? LIke from a manufact ure point of view it doesn't make me any sense, because you are expending more in adding something useless.

Sent from the last layer of Unix Hell. An ubuntu workstation machine.

Nah from arch, but you get the point

seth · Today 07:29:19

You mean CRTCs as equal to CRT monitors ?

https://en.wikipedia.org/wiki/Video_display_controller - it's still referred to as crtc though esp. no cr is usually involved.

I'm understanding that GCN architecture is not supporting analog signals.

That's the $60.00 question - could also just be the dc part of the driver (which is now more or less mandatory) or that was a bug.
We'll seee.

LIke from a manufact ure point of view it doesn't make me any sense, because you are expending more in adding something useless.

Cost cutting because DVI-I connectors are/were more common and you still have a metric shit ton of them.
Do you now scrap them and buy new ones that can't do anything the ones you just discarded can't?

Succulent of your garden · Today 09:31:42

seth wrote:

https://en.wikipedia.org/wiki/Video_display_controller - it's still referred to as crtc though esp. no cr is usually involved.

Thanks!

seth wrote:

Cost cutting because DVI-I connectors are/were more common and you still have a metric shit ton of them.
Do you now scrap them and buy new ones that can't do anything the ones you just discarded can't?

Is this like a marketing move like: Let's put a metal plate inside the hi-fi radio so it adds more weight and people believe that it's better cuz it weights more but the plate is totally useless ? because I imagine back then buying a card and having only a analog monitor and being like fuuuuuuuuuuuuuu.* !!!.

Or if the analog adapter works being like: Let's put more adapters cuz more looks better. Okey add more DVI-I cuz they are cheap.

Arch Linux

#1 Yesterday 02:56:18

Would GPU passthrough for use with a CRT tv be possible on linux?

#2 Yesterday 06:04:48

Re: Would GPU passthrough for use with a CRT tv be possible on linux?

#3 Yesterday 08:07:20

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