Stuck at 800x600 - a puzzle

I’m at a loss. And I believe to have narrowed it down to an issue with the GPU. But I wanted to ask and see if anyone else had an idea for diagnosis.

I have a 5700 XT. I had the HDMI and all 3 DP ports populated going to 3 1080P monitors and a 1080P TV. As none of my monitors had a Display Port, I used DP to HDMI converter cables to accomplish this.
One day DP 3 stopped working at 1080 P and would only output in 800x600. I also noticed that my OS wouldn’t show the name of the device any longer (other outputs would show Sony 1080 P, for example). This would only show a generic “DP-3 800x600”
A few days later, the same fate befell DP-2. And the same for DP-1 shortly after.
I figured at the time this was an issue caused by tinkering with my Arch OS. I booted into Windows to verify or rule out that possibility. In Win10, the 800x600 displays did not show as a display option at all.
I remember that my cables seemed a little warm to the touch at their ends. I’d purchased all 3 DP to HDMI cables at the same time. Figuring they were simply bad, I ordered a new set from a different brand. No luck. Brand new cables did the same thing.
The standard HDMI to HDMI still outputted in 1080P
I updated/reinstalled the 5700XT bios and the MSI x470 Plus firmware. This did not resolve the issue either.
At this time, my WFH job happened to send me a couple cheap HP monitors. And they happened to have Display Port inputs on them.
I connected those to the GPU, and viola, 1080P from all 3 Display Port outputs over a standard DP to DP cable! So the 5700xt does still work on all ports.
Using the DP to HDMI cables (new and old) connecting to the same HP monitors I just received, however, would still only output in 800x600.

I’ve also tried vfio passthrough of the 5700xt to various VMs, same issue on all of those.

As long as a DP to HDMI conversion cable is connected to any of the 3 DP outputs on the 5700XT, it will now only output in 800x600.

So I believe I have done enough experimenting to confirm it’s not an OS issue, and therefore not a driver issue.
This happens on all 6 different model monitors I’ve had access to to try.
This happens on all 3 PCIe slots, with or without a riser cable.
All DP ports are verified to work when using a regular DP cable.
I’ve recently upgraded to a 1000W Seasonic PSU - no change.

The only thing I haven’t been able to try is putting this card on a different motherboard with a different CPU.

I find it especially odd that it used to work, and the issue came up one port at a time.

Have I missed anything? Does anyone have a clue what could be the issue? Does it seem reasonable my 5700XT is just having a bad time?

Forgot to add that I confirmed both the original and second set of DP to HDMI cables are in fact that and not HDMI to DP cables.
Both sets of cables with the same monitors work fine on a 2070 Super.

Sounds like your GPU isn’t correctly utilizing what’s called DP Dual Mode. That’s the bit that’s responsible for converting the DP signal to HDMI for use with a passive adapter like you have.

As for why it quit, it sounds like a hardware issue if the problem persists between different OS’s?

Interesting, I didn’t know that was a feature built into a GPU’s DPs.
In that vein of thought, are there active conversion DP to HDMI cables that would accomplish this if the GPU can not?

There are. DP can even supply power on pin 20 so there isn’t any external power requirement. Just include the tern ‘active’ in your search :+1:.

have you tried attaching signal boosters?
you can get em for a few bux and they just clip over the cable.

your cables are 1.4a or better?
hdmi 2.0 or better?.

if they are earlier versions of the cables you may not have enough throughput for all your screens.

use 1 1080p screen. preferably display port.
set it to 60hz in the screens own menu (if you have that option) and select dp as the default input.

open the pc box, plug the card in to slot 1.

go into bios and set peg 1 as the priority boot.
set pci-e 3.0 or better (if the options there).

reboot into safe mode.
clean out the drivers.
go into control panel device manager and make sure all gfx drivers even the windows or any other vga driver are gone.
reboot into windows.
your screen should be 1080p now.
install fresh drivers.
then reboot.
once done if all is ok add the extra screens one at a time to see if its the load on the gpu output, thats causing the driver to crash and default back to vga 800/600.

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