Troubleshooting: Displayport stuck at 640 x 480

Feb 6, 2007
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So this is a weird one. I just upgraded from a GTX 680 to a GTX 980 ti. The 980 has one DVI port, one HDMI and three Displayports. I currently have the HDMI running to my HDTV/home entertainment center, the DVI to an older BenQ FP241WZ, and a Displayport to a Dell U2412M, with the Dell functioning as the primary display. The Displayport is new for me; the Dell had previously been connected to the 680 via DVI, but that's no longer an option due to a lack of ports on the new card. The HDMI port has to be used for the entertainment center, and the BenQ doesn't have any Displayport connections.

So I typically put the computer (running Windows 7 Ultimate 64 bit) in sleep mode if I'm leaving for a while. I've done this a couple times over the past couple days with the monitors installed in the current configuration, and there hasn't been any issue. Today, my wife turned on the machine, and the resolution on the Dell (connected through Displayport) was locked at 640 x 480, and the BenQ (connected through DVI) had defaulted to primary. The BenQ was still operating at the native resolution of 1920 x 1200. I figured a restart might fix things, but the Dell was still locked at 640 x 480. I tried talking her through various settings in the Nvidia control panel relating to multi-monitor and resolution; I even had her try setting up a custom resolution at 1920x1200@60Hz. Nothing worked. The monitor seems locked at 640 x 480 and won't accept any other signal.

Unfortunately I'm not at home, so I can't actually see the problem firsthand for a few more hours. But is this a known thing? I did some quick Googling and found other people having issues with Displayport connections on Dell monitors. I even went ahead and ordered a Displayport to DVI adapter with the hopes that I can run that to the BenQ and use the DVI port on the graphics card for the Dell (to get Displayport completely out of the question for the Dell). But is there something else I haven't considered? Is this just a known issue with all Displayport connections, and I can't use Sleep mode in Windows 7 anymore? Do newer monitors, especially of the GSync variety, suffer from this issue? I might be looking to upgrade to a newer monitor anyway, and if this is going to continue giving me fits, it may force my hand.

Thoughts, things to try, general information about my predicament?
 

jackstar7

Lifer
Jun 26, 2009
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My one suggestion would be: try and disconnect all other monitors and reboot with only the Dell. Go into Bios really quick and make sure it's showing properly, and then see what happens in Windows.

I've been through my share of monitor issues (even yesterday), but my similar problem was with DVI and an AMD card... so my resolution would likely be no help at all.
 
Feb 6, 2007
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Update in case anyone has this problem down the road. I didn't really solve the issue; the Dell connected via DisplayPort would not register properly coming out of sleep or from a shutdown. The only fix that worked was yanking out the DisplayPort cable and reconnecting it (and I do mean yanking; those things are absurdly hard to remove). I rewired things so the Dell is hooked up via DVI and the BenQ is hooked up via DisplayPort->DVI active adapter and DVI to the monitor. So far that seems to have fixed things. But it's an inelegant solution to a problem that never should have existed in the first place.
 

jackstar7

Lifer
Jun 26, 2009
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Your DP cable shouldn't require a yank, but it does lock in. You just have to make sure you're fully depressing the little bit on one side.

I'm having similar issues I can't track down the cause of since switching to an nV card this week. I have a center DP 3400x1440, then right side is DP 2560x1440 and left is DVI 2560x1440. At random the sides may drop out and be unavailable and it seems agnostic to the input.

DisplayFusion (purchased during steam sale) might also be a factor in some issues... but I haven't been able to count out nV drivers yet. It's just a weird inconsistent issue.
 

flynnsk

Member
Sep 24, 2005
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Not sure if same sort of issue.. I have a Dell U3415W (3440x1440) ultra wide with DP 1.2. If I connect a 2nd DP monitor to the Dell (daisychain), the 2nd monitor ONLY shows 640x480. If I connect 2nd display directly to video card shows correct resolution (2560 x 1400). Going to try a couple more DP cables.. if that doesnt work..may send Dell back :-(
 

jackstar7

Lifer
Jun 26, 2009
11,679
1,944
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Not sure if same sort of issue.. I have a Dell U3415W (3440x1440) ultra wide with DP 1.2. If I connect a 2nd DP monitor to the Dell (daisychain), the 2nd monitor ONLY shows 640x480. If I connect 2nd display directly to video card shows correct resolution (2560 x 1400). Going to try a couple more DP cables.. if that doesnt work..may send Dell back :-(

I would confirm the MST settings. That sounds like a passthrough issue.

Side note: why aren't you just connecting them both to the video card?
 

flynnsk

Member
Sep 24, 2005
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I would confirm the MST settings. That sounds like a passthrough issue.

Side note: why aren't you just connecting them both to the video card?


Yeah, according to the Dell manual, in order to use MST, just need to make sure Display Port is set to 1.2 (it is, comes default at 1.2).

Two reasons, 1st much easier cord management and 2nd is that the Dell is already near the limit of the DP cable length.. the 2nd monitor is just out of reach (about 1.5 feet). daisy chaining from card (DP 1.2a) -> dell (DP 1.2) -> hp (DP 1.1) would be much easier.
 
Feb 6, 2007
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Isn't there a limit to the bandwidth available via DisplayPort? I mean, you're basically asking a single port to carry two 1440p signals; isn't that outside the spec?
 

Viper GTS

Lifer
Oct 13, 1999
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Isn't there a limit to the bandwidth available via DisplayPort? I mean, you're basically asking a single port to carry two 1440p signals; isn't that outside the spec?

Two is fine:

Display-Res-Photo.jpg


From here:

http://www.displayport.org/cables/driving-multiple-displays-from-a-single-displayport-output/

Viper GTS
 

flynnsk

Member
Sep 24, 2005
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Not if one is 3440x1440...

Not an issue of DP bandwidth
http://en.wikipedia.org/wiki/DisplayPort
DP1.2 = 21.6Gbit/s Data= 17.28Gbit/s available video

3440 x 1440 = 4,953,600 Pixels x 60Hz = 297216000 pixels/sec
297216000 x 3 (channels) x 10 bits (per channel) = 8916480000 8.91Gbit/s X2 (displays) = 17.83 Gbit/sec (Raw) X .8 (8b/10) = 14.266Gbit/s

http://downloads.dell.com/Manuals/a...ay/dell-u3415w-monitor_White Papers_en-us.pdf
http://downloads.dell.com/Manuals/a...ay/dell-u3415w-monitor_User's Guide_en-us.pdf
leMmlDYl.jpg


Edit (Again). In case the above manual is not clear enough..means you can have 1 (Source) + 1 (DP Out/External) = 2
 
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