Mac Pro won't run two 30-inch monitors at 2560 X 1600

Discussion in 'Mac Pro' started by Tom762, Feb 24, 2018.

  1. Tom762 macrumors newbie

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    Feb 24, 2018
    #1
    I have a Mac Pro 2.8 mid-2010/Nehalam with a Radeon HD 5770 video card in it (the stock video card for this model) and I’m trying to run two Dell 30-inch U3014 monitors with it.


    This card should easily be able to run the two 30-inch monitors at 2560 X 1600. In fact, I had these two 30-inch monitors plugged into an old G5 with a much less capable video card and it ran them both at high resolution.


    The Radeon 5770 card in the Mac Pro has 1 GB of video memory, and it is advertised as capable of running three 30-inch displays at a resolution of 2560 X 1600. So two should be no problem.


    But only one of my two monitors can get that resolution. The other one shows a lesser 1920 X 1080 resolution.


    The problem might be related to an adapter that I have plugged into one of the card’s ports. The Radeon 5770 has one DVI-D port and two Mini-Display ports. The cables I’m using from the monitors to the card are both DVI-D cables.


    So to be able to plug in the second monitor, I put an Apple Mini-Display-port-to-DVI-D adapter into one of the card’s two Mini-Display ports, and that allows me to plug the second monitor ’s DVI-D cable into the Mini-Display port.


    All the settings on both monitors are identical, but whichever of the two monitors I plug into the adapter is only capable of displaying 1920 X 1080. Yet either monitor will show 2560 X 1600 if I plug it into the card’s DVI-D port.


    So, the problem is not the monitors, and it shouldn't be the video card--- it seems to be the adapter. Is it possible that the Mini-Display-to-DVI-D adapter is not allowing a monitor to show the higher resolution?


    Can anyone tell me how I can run both monitors at 2560 X 1600 with this video card?


    Any help would be much appreciated!


    Tom
     
  2. Darmok N Jalad macrumors 68000

    Darmok N Jalad

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    #2
    I bet it's your adapter. Looks like most mDP to DVI-D adapters have a resolution limit of 1920 x 1200, though knowing your specific brand of adapter would confirm. Can you just go with a straight Display Port cable, or does your second monitor not have that port?
     
  3. Fl0r!an macrumors 6502a

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    #3
    Passive DP adapters are limited to 1080p. To output true dual link DVI you'll need an active DP adapter like this one.

    Using a plain DisplayPort cable is obviously a much better (and much cheaper) solution.
     
  4. Tom762 thread starter macrumors newbie

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    #4
    Thanks for the reply. The adapter is an Apple, the less expensive non-powered version ($35 I think). This Dell 30-inch U3014 monitor seems to have just about every kind of port known to man on the back of it, a whole long row of different shaped ports.

    I found a cable in one of my piles of computer junk that has miniDP on one end and ordinary DP on the other, and when I tried that, I only got a black screen with a message on it that said "no input" or some such thing. That's even worse than the low resolution I had with the adapter, which at least gave me a picture.

    Since the video card on the Mac has miniDP ports, and the Dell display also has a miniDP port, do you suppose a straight miniDP-to-miniDP cable would get me the full resolution? Anyway I just ordered one from Amazon.com that will be here in a few days, and I guess I'll find out then.
    --- Post Merged, Feb 24, 2018 ---
    Thanks! I bet you're right that passive adapters are limited to 1920 X 1280. Since the Mac's video card has a miniDP port, and the Dell monitor also has one, I ordered up a straight miniDP-to-miniDP cable from Amazon.com and I have hopes that it will give me the higher resolution when I connect the Mac to the monitor with it. I'll find out in a few days when the cable gets here. Got my fingers crossed (though it makes it hard to type). Thanks again for the help!
     
  5. Darmok N Jalad macrumors 68000

    Darmok N Jalad

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    #5
    Probably a silly question, but you did make sure you changed the monitor to the Display Port input? It might have still been set to DVI-D.
     
  6. Tom762 thread starter macrumors newbie

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    #6
    Thanks for reminding me to check check that. Yes, on this monitor you can choose input ports in an onscreen menu that can be called up by pushing a button on the front of the display. There are four choices in the Input Source menu: DVI-D, HDMI, DisplayPort, and Mini DisplayPort.

    There is another choice called "Scan Sources" that causes the monitor to detect what port setting to use all by itself, and with the adapter in use, it always chooses DVI-D. If I manually choose any other port, the screen just goes black. So I guess with this adapter it's DVI-D or nothing, with maximum resolution 1920 X 1280.
     
  7. DeltaMac macrumors G3

    DeltaMac

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    #7
    If you have Apple's simple mDP to DVI adapter (the $29 adapter) that allows connection, but provides HD maximum. That is, it does NOT provide the dual-link connection that you need to get the full 2560 x 1600. You need the active adapter that gives mDP to dual-link DVI (for $99). Whatever you use needs to provide support for dual-link DVI. The cheap adapter does not do that, which will explain why you only get 1920 x 1200

    Another (cheaper) alternative is to use a mini DisplayPort to DisplayPort cable. I THINK your Dell U3014 came with one of those from the factory. Does that not work for you? (much cheaper than the $100 dual-link DVI adapter :cool: )
     
  8. Tom762 thread starter macrumors newbie

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    #8
    Thanks for the suggestion, but as I said above, I found a cable like that among my tangle of cables in a drawer. It has a miniDP plug on one end and a regular DP on the other, but when I hooked it up between the Mac and the monitor, all I got was a black screen. There was a message on the black screen that said "No Input."

    So I guess that particular combination of out and in ports is a no go. I'm beginning to think that this monitor is not going to be happy until the cable that connects it to the Mac has the exact same kind of plug on both ends. And since the Mac's card has a miniDP port, and the monitor has one too, it's going to have to be miniDP to miniDP.

    Fortunately, such a cable on Amazon.com only costs $7.00, and I've got one coming now. So along about Tuesday I'll find out if that cable will provide the full resolution of this monitor.
     
  9. DeltaMac macrumors G3

    DeltaMac

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    #9
    OK. I'm guessing that you did try changing the Input Source menu (on the display) to DisplayPort (?)
    Did you also try BOTH mDP ports on the MacPro vid card?
     
  10. Tom762 thread starter macrumors newbie

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    Feb 24, 2018
    #10
    Yes, thanks, I have tried the adapter in both of the miniDP ports in the Mac's card, and the result is the same: both ports work, but the max resolution is only 1920 by 1080.

    And I tried choosing each one of the four input sources on the monitor's user menu: DVI-D, HDMI, DisplayPort, and Mini DisplayPort, but only the DVI-D input choice results in an image on the monitor.

    There is another menu choice called "Scan Sources," which allows the monitor pick the port it detects as being in use, and when I choose that, the monitor always picks DVI-D as the input source.

    So I guess that about exhausts all the possibilities with the cables I have. Looks like it's boiling down to waiting for that miniDP-to-miniDP cable that I have coming in the mail next Tuesday, and hoping it will provide full resolution on the monitor.
     
  11. DeltaMac macrumors G3

    DeltaMac

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    #11
    I wan't clear on my question, I suppose.
    I was asking about the mDP to DP cable, not the limited adapter that you already know doesn't work to give full resolution with DVI-D.
    (So you now have found out, it's the adapter that limits you, not the port itself)

    I hope that you disconnected the adapter, and tried the mDP to DP on both ports of the graphics card, and also tried the various alternative settings with THAT cable, too.

    You have TWO identical Dell displays - so, you should have a second mDP to DP cable, too! Might be worth trying a different cable, if you can find it ;)

    And, you might even try swapping the displays, just in case one display has a bad DP port
     
  12. Tom762 thread starter macrumors newbie

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    #12

    Thanks again. The Radeon 5770 card in this Mac Pro has one DVI-D and two miniDP ports. So the first monitor has a straight DVI-D to DVI-D cable connected to the card's DVI-D port and it works fine.

    In fact, the old G5 Mac that I was using these two monitors with before had two identical DVI-D ports on its video card, so I had both monitors hooked up with identical DVI-D cables, and they both had 2500 X 1600 resolution and worked great.

    So now I go and give up my faithful old G5 that I've used for all these years and move up to a Mac Pro, and I try to connect the two monitors to it. And does the video card in the Mac Pro have two nice big fat DVI-D ports on it like the old G5's did, as (I think) it properly should? No such luck!

    Instead it's got a mixture of port types: only one DVI-D, plus two miniDP. Hence the necessity for an adapter to a miniDP port to use the second DVI-D cable, and all this trouble getting the high resolution back (grumble, grumble).

    But your idea is good--when I tried the miniDP to DP cable, I did try it with all the input ports on the monitor's menu settings, but I don't think I tried plugging it into both of the miniDP ports on the Mac. So I'll go back and do that now. Thanks for the suggestion. I appreciate the help. I'll report results.
     
  13. ActionableMango macrumors G3

    ActionableMango

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    #13
    Use your monitor's on screen menu to set your monitor to Display Port 1.1.
     
  14. Tom762 thread starter macrumors newbie

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    Feb 24, 2018
    #14
    Thanks. In the menu I see the option of setting DisplayPort to 1.2, but not 1.1.

    I "enabled" DisplayPort 1.2, but nothing changed. What does that do?
     
  15. phairphan macrumors 6502a

    phairphan

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    #15
    It sounds like you may be testing this with one monitor connected to the DVI port. If so, make sure that the mDP to DVI adaptor is unplugged from the card when you try the DP cable. The 5770 was a bit confusing in the number of monitors it could support. I believe that it only supported two ports when using legacy connection methods. If you have a monitor plugged into the DVI port and the mDP to DVI adaptor plugged into one of the mDPs, I believe that it may disable the remaining mDP.
     
  16. Fl0r!an macrumors 6502a

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    #16
    It's a new newer specification of the DisplayPort standard which allows for higher resolutions and daisy chaining of displays. Your HD 5770 doesn't support DP1.2, so it's important to keep it disabled!

    Also make sure that you're plugging the DP cable in the DP input of your display! It also has a DP output (meant for daisy chaining multiple displays), which can't be used as input!
     
  17. Tom762 thread starter macrumors newbie

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    #17
    Thanks phairphan, I'll do as you say and make sure the adapter is unplugged when I try the cable again that has a mini-DisplayPort plug on one end for the video card and a regular display plug on the other for the monitor. It's about 3 AM here right now so I'm headed off to bed and I'll try that cable again when I get up.

    It doesn't matter to me if only one of the mini-DisplayPorts works at a time, since I'll never connect a third monitor to the card anyway. But I see what you mean--if the adapter was in one of the mini-DP ports, the other mini-DP port might not work when I try the cable in it (assuming it was going to work). Thanks for letting me know that.
    --- Post Merged, Feb 25, 2018 ---
    Hey, now that's a thought! I didn't know that this monitor had a DP output port. I thought all the ports were input ports. They are so hard to see and get at up underneath the back of the monitor that I had to use a mirror to see where they all are.

    After I spotted a DP port I had my wife reach up underneath where the ports are, while I tipped the monitor forward to make it a little easier for her, and she plugged the cable into a DP port with her nimble little fingers.

    I really don't know what port she put it into, except that it was a DP port, and the cable plugged right into it. It could very well have been an output port. Everything is black and the black-on-black lettering is hard to read.

    When I get up in the morning we'll do it all over again and this time we'll make sure that the DV port says "INPUT" on it. I will report the results here.

    And as you suggested, I went back into the user menu and disabled the DP 1.2 feature. Thanks for telling me about that. I'm so danged ignorant about these things. I sure appreciate the help I'm getting from you and other kind people on this forum. Thanks again!
     
  18. Darmok N Jalad macrumors 68000

    Darmok N Jalad

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    #18
    Just wondering, have you tried swapping cables between the 2 monitors? Maybe your other monitor will accept the display port connection. It’s a long shot, but maybe one of your monitors has a bad port?
     
  19. hwojtek, Feb 25, 2018
    Last edited: Feb 25, 2018

    hwojtek macrumors 65816

    hwojtek

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  20. Tom762 thread starter macrumors newbie

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    #20
    Thanks again.
    PROBLEM SOLVED! You were absolutely right Darmok, we had the miniDP to DP cable plugged into the OUT port of the monitor the last time we tried it! Before we tried again this morning, I downloaded the monitor's user manual from the Dell site and it contained a good photo of all the ports.

    That photo showed us which are the IN ports and which are the OUT, which is hard to tell on the real monitor because everything is black plastic, and it's also dark up under where the ports are (you need a flashlight and a mirror to see them). The manual's photo shows that the IN port is the one nearest to the power cord, and of course it's the one that is the most difficult to see.

    So we tried the cable again, and this time we made sure that the DP end of it got plugged into the monitor's IN port, and VOILA! FULL RESOLUTION on the monitor! Success! Now I have two hi-res monitors again, and all is well with the world!

    I never would have known that I'd plugged the cable into an OUT port if you hadn't mentioned it, Darmok, because until you told me otherwise I had thought that ALL those monitor ports were IN ports. And naturally, Murphy's Law decrees that if there is a right choice and a wrong one, the wrong one will always be picked first, which is just what we did yesterday.

    Thanks a million, and thanks again to everyone who helped me out with this problem. I am very grateful for all the assistance. This is a great forum!
     
  21. itdk92 macrumors 6502

    itdk92

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    #21
    Needs to be the full fledged 100$ version.
    The 35$ version is single DVI, the 100$ version is the dual link DVI.
     
  22. Tom762 thread starter macrumors newbie

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    Feb 24, 2018
    #22
    Yes, I guess it would have had to be the more expensive version, if I had to get an adapter.

    Thankfully, no adapter is required now, since as I posted above, the cable I found with a miniDP plug on one end (for the computer's video card) and a regular DisplayPort plug on the other end (for the monitor) turned out to work, after I plugged it into an IN port instead of an OUT port like I did yesterday. Problem solved! Thanks for the info though!
     
  23. Darmok N Jalad macrumors 68000

    Darmok N Jalad

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    #23
    As much as I'd like to take credit for the in/out port comment, I believe that credit goes to Fl0r!an. Glad you got it sorted out!
     
  24. Tom762 thread starter macrumors newbie

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    #24
    Ah yes, I got confused: THANK YOU Fl0r!an! But you helped plenty too and I appreciate it. I have a much better understanding now of how monitors, video cards, adapters, and cables all interface.

    I used my old G5 Quad from 2005 until now, and making the change from a PowerPC to a Mac Pro has been fraught with these kinds of problems. This monitor trouble was only one of them. I hope I don't have to switch to a different Mac for another ten years or so, especially one with a different kind of video card. I don't want to go through all this again.

    But now this Mac Pro has two big beautiful 30-inch monitors running with it at full resolution, so thanks to everybody here, that problem is solved. What I really like about the Mac Pro is that it is quiet. Did you ever hear a G5 Quad trying to keep itself cool?

    Those things ran HOT, all the time, and so Apple provided them with dozens (it seemed) of big internal fans that howled all day long, like a vacuum cleaner at close range (the hot air exhaust did make the Mac a good heater in the winter, though).

    But ah, now I sit in front of these two big monitors (both at full resolution--thanks again!) next to a whisper-quiet computer. The silence is almost deafening after what I've been used to. I love it.

    Thanks again everybody.
     
  25. Darmok N Jalad macrumors 68000

    Darmok N Jalad

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    #25
    Heh, yeah, I owned a Dual G5 1.8GHz a long time ago. I remember the fans going full bore. The Mac Pros just don't ever come close!
     

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