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Newer Radeon video cards come with four ports standard:

  • DVI (x2)
  • HDMI
  • DisplayPort

enter image description here

If I want to run three 24" monitors, all of which are DVI only, from this video card -- is it possible to convert either the HDMI or DisplayPort to DVI? If so, how? And which one is easier/cheaper to convert?

I did a little research and it looks like there isn't a simple "dongle" method. I found this DisplayPort to DVI-D Dual Link Adapter but it's $120; almost cheaper to buy a new monitor that supports HDMI or DisplayPort inputs at that point!

There's also a HDMI to DVI-D adapter at Monoprice but I'm not sure it will work, either.

AnandTech seems to imply that you do need the DisplayPort-to-DVI:

The only catch to this specific port layout is that the card still only has enough TMDS transmitters for two ports. So you can use 2x DVI or 1x DVI + HDMI, but not 2x DVI + HDMI. For 3 DVI-derived ports, you will need an active DisplayPort-to-DVI adapter.

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So although HDMI is pin compatible w/ DVI the card itself can only drive two of the single HDMI and dual DVI ports at a time? That stinks! I trust Monoprice on their cable and hardwares. How about instead of buying another monitor you add another video card? Depends what you are doing w/ the third monitor... –  mindless.panda Mar 12 '10 at 2:50
    
Dell Optiplex 960 has the same problem - two TDMS drivers, but three ports. Only two will work at the same time. –  staticsan Mar 25 '10 at 0:04
    
Or, instead of paying more money for an adapter, you could just buy another video card card (old school PCI even) for cheaper –  Allen Apr 7 '10 at 20:54
    
OK, so the card can only power two digital outputs at once. Are there any consumer cards out there (mainstream-ish, not like $500+) that support 3 or more at once, without sapping USB power? –  Coderer Apr 27 '10 at 17:09
    
@coderer it supports 3 digital outputs, it's just that 2 of them have to be DVI and one has to be DisplayPort. –  Jeff Atwood Apr 28 '10 at 8:36
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4 Answers

up vote 8 down vote accepted

From what I heard, the cheap adapters don't work because you need something that generates an TDMS Signal. The cheap adapters expect the source to already support a TDMS Signal and more or less just convert mechanically.

I have a post here. I ended up buying a $100 Dell Adapter which works, but fails whenever power savings comes into play (I basically have to unplug/replug to "reset" the adapter).

In hindsight, I would have bought a Display Port Monitor or a second card, both options would have been cheaper and less problematic than the Adapter, but I already had 3 screens.

Edit: After 2 Weeks, I really regret it. The adapter just "crashes" after some time (black screen, sometimes it turns on, off, on, off... My Monitor always stays on, so it's the adapter not generating a picture signal anymore). I'll try a USB-Charger next as they hopefully have more power, but I now really regret not getting a DP Monitor instead.

Video of DisplayPort-DVI Adapter Suckage: http://vimeo.com/10425439

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how problematic are we talking for the adapter? Can't you disable power saving for USB? –  Jeff Atwood Mar 12 '10 at 2:49
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USB is only used for Power (so it's invisible to the system), it's the normal sleep or turn off monitor mode that seems to cause issues. Not using hibernate, but if I leave my PC for 30 minutes or so, My screen turns black, shows picture, turns black, shows picture. I might put it into a USB/110V Wallplug. The issues seems to be (from reviews) that they draw too much power. I'm running a 24" at 1920x1200. –  Michael Stum Mar 12 '10 at 2:53
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See the Reviews on the Dell Site: accessories.us.dell.com/sna/products/Cables/… –  Michael Stum Mar 12 '10 at 2:55
    
See my answer, a relatively cheap ($20 vs $100, not as cheap as the $3 HDMI->DVI adaptors though) DisplayPort->VGA adapter should work. –  davr Mar 25 '10 at 0:02
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If you can live with 1920x1200 resolution:
HDMI to DVI Cables for $20+
DisplayPort to DVI Cable for $30+
If you want 2560x1600, you need an active adapter.

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looks like you're right, active conversion from DisplayPort to DVI is the only way to get this to work -- I found another active DisplayPort to DVI-D adapter with favorable reviews on Amazon. –  Jeff Atwood Mar 12 '10 at 1:51
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Yeah, the way the Radeon hardware works, is that one display circuitry drives both the DVI2 and the HDMI port. So you can't have them both hooked up at the same time. Therefore to get 3 monitors, you have to do DVI+DVI+DisplayPort, or DVI+HDMI+DisplayPort. DVI+DVI+HDMI is unfortunately NOT an option.

I believe the DisplayPort to VGA adaptors for ~$20 should work, if you can live with an analog signal on your 3rd monitor that's limited to 1920x1080 or 1920x1200 (most monitors are this size or smaller anyway still). The reviews on monoprice show it worked for 3 people with this card, but did not work for one person with this card.

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Interesting. I'm guessing these work because they have the mentioned chip that actually converts the signal. The only downside is that they are VGA, which is a Sin. –  Michael Stum Mar 25 '10 at 5:23
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This is a more general answer regarding being able to use HDMI-to-DVI adapters and ignoring your specific problem (described on the Andantech page you linked to (paragraph starting with "Making 4 ports fit on a card...").

With my graphics card (Geforce GTX 275) I got an HDMI-to-DVI adapter which looks like the "HDMI Male to DVI-D Female adapter" at monoprice.com and works fine.

So unless there is a limitation like you have it an HDMI-to-DVI adapter should work, too.

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You adapter is mechanically DVI-D, but electrically it's a Single link. –  Chris S Mar 12 '10 at 15:03
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