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I have a AMD Radeon HD 6800 Series graphics card which has 2 DVI outputs. I tried to set it up with 2 monitors which both have vga connectors on the end and used 2 dvi to vga adapters like these.

http://www.tvcables.co.uk/images/items/vga-to-dvi.jpg

For some reason nothing would reach the monitor, it would remain in standby, if it was plugged into the second output. I tried all the different combinations of cables, adapters and the 2 monitors but whichever monitor that was plugged into the second output wouldn't work.

I then randomly decided to plug a different monitor into the second output which has a dvi connector on the end so there was no need for an adapter and plugged it in and it worked!

Does anyone know why the second output on the graphics card won't work with a dvi to vga adapter (and the first output will)? I'm really confused!

Thanks

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It may only be a DVI-D port. –  Shinrai Apr 4 '12 at 16:07
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1 Answer

up vote 3 down vote accepted

There are a variety of DVI ports which support different connections. The ATI 6800 series cards commonly have the following DVI connections:

  • one DL-DVI-I
  • one SL-DVI-D

DL is dual link which provides support for higher resolution like 2560x1600, SL is single link which doesn't support higher resolutions like 2560x1600, DVI is the connector form factor, I is integrated digital and analog support and D is digital only support

So only the first supports an analog connection using a simple adapter.

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Thanks. That's really interesting. Does this mean then that the graphics card actually detects that an adapter is plugged in and will output differently through it? –  Tom Jenkinson Apr 5 '12 at 10:21
    
also is VGA analog? –  Tom Jenkinson Apr 5 '12 at 10:28
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The graphics adapter detects what type of monitor is attached and outputs the appropriate signal if it's supported by that connector. Yes VGA is analog. –  Brian Apr 5 '12 at 12:45
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