AM5 and 4090 problem

[Javier López]

Hi: Has anyone tried the combination of 7800x3d + 4090 + 3 tvs?
I have that combination and is impossible to get 120 hz and full rgb color (only ycbr 422 o 420 in one, two or the three screens, normally the three). However, no problem getting the 120 hz and full rgb color with a 3090 and an AMD RX 6800 in the same rig. By the way, the 4090 works flawlessly on an old intel pc. I tried two differents 4090 to no avail.

 

[Javier López]

Hi: Has anyone tried the combination of 7800x3d + 4090 + 3 tvs?
I have that combination and is impossible to get 120 hz and full rgb color (only ycbr 422 o 420 in one, two or the three screens, normally the three). However, no problem getting the 120 hz and full rgb color with a 3090 and an AMD RX 6800 in the same rig. By the way, the 4090 works flawlessly on an old intel pc. I tried two differents 4090 to no avail.

Really nobody knows a friend or a youtuber with that combo?

 

[Novopaine]

Unfortunately I don't have any experience with a 4090, I have a 7900XTX. But I find it unlikely this to be related to the CPU. The operating system itself, maybe. I would consider filling out a bug report with Nvidia, or maybe post the issue on their forums. https://www.nvidia.com/en-us/forums/

 

[Durge Driven]

Could this possibly be down to your display leads.

 

[Javier López]

Thanks Novopaine and Durge Drive for your replies.
I think the operating system is not at fault: I've installed Windows 10 (two times, clean install) and 11 to no avail. Also I've updated the vbios and the motherboard bios two times each. I made contact with Nvidia, they only requested the msinfo file and found nothing of interest in it. As I'm using 3 tvs I have to resort to adapters (displayport 1.4 to hdmi2.1) . The two 4090, the 3090 and 6800 run without problem in an old intel pc. With AM5 only the 3090 and the 6800 work, getting the 120hz and full rgb color. By the way the motherboard is a Gigabyte b650 aorus elite ax, nvme 4tb, 32gb ram cl 30, 1000w psu corsair. Regards

 

[Novopaine]

It's possible that something else is limiting you, like maybe the color depth setting.

Example: 12bpc, 10bpc, 8bpc, etc. If it's set to 12bpc, try lowering it to 10bpc to see if that unlocks the Full RGB.

 

[Spinelli]

I've seen issues like this in the past. Nothing to do with operating system or CPU. It has to do with something in the video "line". GPU, cables, adapters, monitor/TV, etc. Most people I've seen with this issue, or similar issue, are using the following combination: 3x Televisions (not PC monitors), 3x 4K resolution, at least 1 of the TV's is hooked up with a video input adapter.

First thing I'd try is, in Nvidia control panel, lowering all screens to 8-bit. 99% of games are created in 8-bit. Even with games created with 10-bit and HDR, I'd challenge anyone to notice the difference without side-by-side screenshots.

Also, I wouldn't worry much about YCBR422. Almost impossible to tell the difference between it and full RBG. Definitely avoid YCBR420 though. The differences between YCBR420 and the others is quite noticeable.

 

[Javier López]

It's set to 8 bpc. Also I tried nine or ten nvidia drivers with the same result. The seller tested the first 4090 recreating a similar environment, AM5 motherboard, etc. and couldn't get 120 hz and full rgb color, so they sent me a new one. The thing is, I've been asking the seller about what motherboard was used to run the test, because if it was the same motherboard I have, maybe a different mb could solve the problem. Curiously, the only answer I get from them is "it was tested in a similar environment like you have, AM5". Regards

 

[Javier López]

Spinelli: I have to disagree, I can tell the difference between ycbr422 and full rgb color The 3 tvs setup is a pain, I've been doing it since 2012 until now, though

 

[Spinelli]

It's set to 8 bpc. Also I tried nine or ten nvidia drivers with the same result. The seller tested the first 4090 recreating a similar environment, AM5 motherboard, etc. and couldn't get 120 hz and full rgb color, so they sent me a new one. The thing is, I've been asking the seller about what motherboard was used to run the test, because if it was the same motherboard I have, maybe a different mb could solve the problem. Curiously, the only answer I get from them is "it was tested in a similar environment like you have, AM5". Regards

I'm 90% sure this has nothing to do with motherboards. It has to do with GPU, cables, adapters, and TVs. I've seen lots of other people have issues when trying to run triple 4K + HDMI + adapter/s + 120 Hz televisions. Strangely, they were mostly (or all) Nvidia GPU users, not AMD. I wish I could help you more. Are you sure the adapter is good? Is it an active adapter? Are all HDMI cables 2.1? Is the DP cable 1.4? Do you know if DP DSC is being used (DSC shouldn't be required for 4K, 120 Hz, 8-bit, RGB)?

 

[Javier López]

Thanks for your help, Spinelli. Well, three Cable Matters adapters dp 1.4 to 8k, three Snowkids hdmi 2.1 cables. I think they're working fine, right now I'm writing on the intel socket with the 4090 getting 120 hz and full rgb color at 11560x2160 resolution and g-sync enabled. I can't see the word 'active' on the adapters nor in its advertising, though. I guess the DSC is not enabled, because I can't see in the Nvidia Control Panel Image Scaling, only Image Sharpening and I think the AM5 socket had the same, I'm not sure though, maybe I have to give it a try again. If the DSC was enabled, how to disable it? Regards