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I have two computers connected to a Dell U2711 monitor. A PC which is connected using DisplayPort and a Mac connected using DVI-D.

The PC displays 2560 x 1440 resolutions perfectly but when I try and set that resolution on the Mac it displays in an extremely fuzzy manner. So fuzzy in fact that I can hardly read the text on the screen.

I've tried the Mac out connected via DisplayPort (unfortunately the monitor only has one DisplayPort connection) and it worked perfectly. I also had it connected via DVI-D in the past and it worked then. For some reason it just does not work anymore.

I was wondering if this problem might be caused by a dodgy cable or perhaps not having the correct one.

Can anyone think of what the issue might be? I've checked out the DVI-D spec and it should be able to display resolutions of 2560 x 1440 correctly.

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1  
Do you use a dual-link DVI capable cable with a full 8x3 pin array? – Daniel Beck Oct 3 '12 at 19:48
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Did you use the same cable as you used in the past? If not, was the old DVI cable dual link and us the new cable single link? (See en.wikipedia.org/w/… ) – Hennes Oct 3 '12 at 19:49
    
@Hennes Ah that was it. I feel like a fool now. I was trying to use a DVI-D single link cable rather than a double link cable. Thank you both for the help :). – Cromulent Oct 3 '12 at 20:20
up vote 1 down vote accepted

Higher resolutions and refresh rates require a Dual Link DVI cable.

  • DVI-I includes analog signals so can be used with a DVI to VGA passive adapter.
  • DVI-D is digital only and can't be used with a VGA passive adapter

  • Single Link can't do higher resolutions and refresh rates.

  • Dual Link can do higher resolutions and refresh rates.

enter image description here

Image from Wikipedia article: Digital Visual Interface

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