Topic Title: 2 GB GDDR5 AMD Radeon HD 7870 - Problem with two 30 inch monitors - Help me with my wife!
Topic Summary: Issue with 2nd monitor is blury
Created On: 07/23/2013 10:09 AM
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 07/23/2013 10:09 AM
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I was running one, 30 inch monitor using a 2 GB GDDR5 AMD Radeon HD 7870.  I was using the HDMI cord.  All was GREAT.

Last night I added a second, 30 inch monitor using the SAME 2 GB GDDR5 AMD Radeon HD 7870.  

Due to cable length, the new monitor is now attached with the HDMI.  All is GREAT on this monitor.

However, the original 30 inch monitor that was previously perect and that is now attached using a non-HDMI cable is now blurry.

I know both monitors are good.  The new monitor is perfect with the HDMI cable.  The "old" monitor that was perfect is now the blurry one.  

Please help.  My wife is looking at me like an idiot that spent a bunch of money on a second monitor and created a huge problem.  

Do I need to purchase a second graphics card? 


 07/23/2013 11:27 AM
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Detail exactly how both 30" monitors are now connected.  What Catalyst Driver version are you using?

What is the specific brand/model if each 30" monitor?



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 07/23/2013 11:35 AM
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The 2 monitors are Dell Monitors.  In particular - UltraSharp U3011 30-inch Widescreen Flat Panel Monitor.

1 monitor is connected with the HDMI cable.  The second monitor (blurry monitor) is connected with a non-HDMI cable.  I forget which cable.  I do not know which driver I'm using.  (I'm at work now and not home with the monitors)

Someone at work suggested that I try a a DVI-HDMI adapter.

 07/23/2013 05:10 PM
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By "blurry", I'm going to assume you mean it got stuck at a lower resolution.

It may be a driver bug, where it forgets that HDMI 1.3 supports the native resolution of those monitors.  Or it might be some kind of hardware limitation, where HDMI 1.3 is only supported if the DVI-D isn't used.  I just don't know the details well enough to guess.

But I can tell you how to get the two monitors working perfectly, though not precisely, because you did not indicate exactly what graphics card you have (there are many 7870 models available, with different connector options).

The short answer is, use only DisplayPort or Dual-Link DVI-D to connect the monitors. 

The longer answer depends on what connectors you have available.  In general, the card will have either one normal DisplayPort connector, or two mini-DisplayPort connectors.  They are electrically compatible, so a simple passive adapter will convert between the two.  The card will also have one or two DVI connectors, though only one of them will be Dual-Link.

If your card has only one DisplayPort connector, then you will have to use DVI as well.  If the card has two DVI ports, you must determine which one is Dual-Link.  In every case I've found, this will also be the one port that also supports analog VGA.  If the same connector part is used on each, look for "VGA" next to one.  If the connectors are different, look for the one that matches Dual-Link DVI-I here.  Make sure you have a Dual-Link DVI cable.  There should be no gap in the middle of the pins, as you see in the Single-Link picture at the Wikipedia link.  Dual-Link DVI-D is fine, since you won't be using the analog pins.

If you have two mini-DisplayPort connectors, you can run both monitors that way.  Use either DisplayPort to mini-DisplayPort cables, or normal DisplayPort cables with adapters to reduce the connector on one end to mini-DisplayPort.  If just the one connector, use a normal DisplayPort cable.

As to which monitor you plug in where, it doesn't matter.  One will be labelled #1, and one #2, but they can be arranged however you like.


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