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mikewinddale
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DisplayPort problems - artifacting

Mon Dec 24, 2018 5:11 am

So yesterday, I just built myself a new system with a Radeon RX 580. I spent this morning benching it on 3DMark with no problems.

Then tonight, when I benched 3DMark again, I'd suddenly get horrible artifacting. Basically, the screen would be split into several distinct strips, and each strip would independently jitter and artifact. The artifacting was so bad, and the strips were so distinct, that you couldn't even tell each strip was part of the same image as another strip.

I exited 3DMark and re-ran it several times, and the same thing happened every time. I checked my GPU temps, and they weren't getting above 75C.

Then, I tried playing Starcraft 2. For the first several minutes it was fine, and then the exact same thing happened.

Meanwhile, I had a second monitor, and none of this was happening. I would be getting artifacting on the first display while the second display still looked fine.

For example, when SC2 blew up and I exited to the desktop, the primary display was still artifacting while showing the Windows desktop, but the secondary display was displaying the desktop just fine.

Then I realized the first display was using DisplayPort while the second display was using HDMI. Maybe that was the culprit? So I connected the first display to HDMI and disconnected the second display. (The second monitor only accepts HDMI, so I can't simply swap them.)

I ran 3DMark again, and this time, no problems. Then I played SC2 again - no problems.

So switching from DP to HDMI seems to have solved the problem. But it means I can't have a multi-monitor setup anymore, since the Radeon has only one HDMI.

Also, I want to know *why* DP isn't working. Is it a defective graphics card? Defective cable? I can live with a defective cable, since I can just buy a new one. But I don't want a defective graphics card!

I'm seeing stories online of people with DP problems being told to get better cables. One article even says that gas-operated chairs (like mine) can create EMI that can interfere with DP. (https://support.displaylink.com/knowled ... ing-or-los)

So I've just ordered another DP cable from a different company, plus an active DP-to-HDMI converter from a third company.

But before I go spend a million dollars on different cables, I want to see if anyone has any other suggestions for how I might diagnose this problem.

Thanks.
 
Topinio
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Re: DisplayPort problems - artifacting

Mon Dec 24, 2018 7:27 am

DP cables are fairly length-sensitive, and the various (earlier) versions of the spec IIRC could be an issue if only up to 1.1 (?) is supported by the GPU or the monitor. If you're doing MST or high res/refresh, there's some need to think about bandwidth, too, as you can see the picture but with artifacts if your bandwidth requirements are not supported by the cable (e.g. the cable can only do RBR at the length and you're trying to use it for a res/refresh which needs HBR; or HRB2 vs HBR). Higher spec cabling definitely can help with DP connections.

That said, the only times I've seen a card start to deliver the picture with artifacts after previously being fine have (sadly) been when it's been cooked in some way.
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Mentawl
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Re: DisplayPort problems - artifacting

Mon Dec 24, 2018 9:18 am

I've had DP cable issues with my 27" Dell 2560*1440 screen in the past - one of the cables I tried just reset the monitor constantly (as if it were switching resolutions), which was very strange. The cable previously worked ok with a 1920*1200 screen.

Using the cable that Dell supplied with the 27" screen worked fine, as did a new longer high-quality one I purchased (my screen is a coupl've meters from my PC).

I'd definitely suspect the cable initially, pick a decent branded one of the correct length and you should hopefully be all good :) if in doubt check https://www.displayport.org/product-cat ... -adaptors/ for advice and options.
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JustAnEngineer
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Re: DisplayPort problems - artifacting

Mon Dec 24, 2018 9:30 am

I'll support the idea of trying a good quality DisplayPort cable.

Have you tried one of the other DisplayPort outputs on your graphics card?

Have you looked at the graphics card's temperature and fan speed trends in Wattman?
(Right-click, AMD Radeon Settings, Gaming, Global Settings, Global Wattman)
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Re: DisplayPort problems - artifacting

Mon Dec 24, 2018 10:01 am

I'd try a different cable first, but it sounds like it may be a problem with the DP output on your card. If you have access to another device with a DP output I suggest you test the monitor on that to rule out potential issues with the DP input on the monitor.
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