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Just got new pc with 2 x Gigabyte AMD Radeon HD 7850 cards that are bridged using the included CrossFireX/SLI connector.

I have 2 monitors that are exactly the same, and they both have vga connectors with DVI converters attached.

I've plugged the one monitor into the first graphic cards' DVI port and the second in the second graphic cards' DVI port, but only the first cards' monitor is displaying in Windows 7. The Catalyst control center are not picking up the second monitor.

Any suggestions, please, on how to use the 2nd monitor on the second card?

Thank you!

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Plug both monitors in the same graphics card. The second card is only for calculations. Not for outputting video. –  Hennes Oct 19 '12 at 19:17
    
OK, so I need to get a dvi to HDMI converter in that case, since the card only has one dvi input. Thank you! –  Pieter Oct 19 '12 at 19:21
    
Note, you can't go HDMI -> DVI -> VGA. VGA is analog, while HDMI is digital. The DVI ports are special in that they transmit both analog and digital signals. You have to get a special converter to change HDMI's digital signal into analog before it can be run to VGA. –  Darth Android Oct 19 '12 at 19:43
    
The card also has 2 Mini DisplayPorts, I think this is my solution : hdcabling.co.za/… –  Pieter Oct 19 '12 at 19:50

1 Answer 1

up vote 0 down vote accepted

Let me post this as a full answer and add some deatils.

Thing to realise when using Crossfire (AMD) or SLI (Nvidia):

  1. Only one card gets use to output the graphics. The other cards are just used in calculations.
  2. RAM is not additive. (Two 1 GB cards will yield a 1GB crossfire situation, despite a total if 2GB if you sum the memory. Same for 2+2=2, 1+2=1, etc. etc.)

Output:

  • VGA is analog only.
  • DVI can do both analog or digital. But there are versions which do onlY digital.
    Wikipedia has a nice article on this
  • HDMI is digital only (Basically digital HDMI + sound + optional encryption)
  • Displayport is digital only.

If both your monitors use the ancient DB15/VGA connector then you will need to convert two signals to analog. One is easy, via a dual signal DVI to VGA connector. The other will need a convertor from miniDisplayport to DVI-A (analog only) or DVI-I (both digital and analog). The convertor/cable you listed will convert to DVI-D (Digital only). A simple cable to from DVI-D to VGA is not going to work.

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Thanks for the great feedback. The card also has a HDMI out. Will this cable/converter work? hdcabling.co.za/… –  Pieter Oct 20 '12 at 3:25
    
It should work if your display uses 1920x1200 or less. –  Hennes Oct 20 '12 at 3:37
    
Excellent! Thank you very much for the great answer and explanation –  Pieter Oct 20 '12 at 3:38

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