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It seems that pure 2 x DVI dual head video cards are becoming rare. Most cards feature something like 1 x DVI plus 1 x HDMI plus 1 x VGA or some other interface. The idea seems to be that you can just use an HDMI <=> DVI adapter.

One result is that cards are seldom marked " 2 x DVI " anymore, but does this mean that they support simultaneous output on all interfaces? Are all cards dual head these days?

Take Asus's nVidia cards for example, they routinely have 1 x DVI plus 1 x HDMI instead of 2 x DVI, so my question is, are these equivalent to a dual head DVI card, or is there some detail required for dual monitor support?

I use dual-monitor stretched desktops for digital signage projects.

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4 Answers 4

up vote 5 down vote accepted

Yes they are dual monitor cards. HDMI uses the same signal as DVI in a different connect (plus it adds audio support). An HDMI-> DVI adapter is just a pin converter nothing more.

So yes a DVI + HDMI card will drive two DVI monitors without a problem, or two HDMI monitors for that matter.

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With the caveat that those converters are HDMI -> single link DVI. –  Ben Voigt Dec 24 '12 at 4:02

Most of these cards, and all of the latest Nvidia cards I have used do support dual (or triple) output no problem - without even breaking a sweat.

DVI and HDMI are pin compatible and you only need the cheapest of adapters in order to output to the other as you said.

So, yes, these are the equivalent to dual head cards.

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Two perfectly good, functionally eqiuvalent answers, but I thought shf301 could use the rep :-) –  nray Nov 14 '09 at 18:11

You can get dual monitor, but tripple monitor (even with 3 heads on your card) is not always a guarantee, as I found out painfully, recently when I bought an HDMI/DVI/VGA card. It would only allow DVI or HDMI, not both, you have to disable one port to enable the other.

It was an ATI card -- strangely, the same chipset is used in a DisplayPort card (DisplayPort, DVI, and VGA) and it DOES support the use of 3 monitors.

Bottom line, if you want to run THREE monitors, make sure the card you buy actually supports it, and isn't just a dual monitor card with 3 heads -- and not just the chipset, but the exact card you buy.

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Maybe some custom drivers will enable the feature? –  surfasb Apr 22 '11 at 20:57
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I don't think so, I did a lot of digging and could not find any custom drivers or firmware that enabled it. From all the digging I did, my problem seems to be very specific to my hardware. I think it had something to do with the amount of clock signal generators (sorry, I'm fuzzy on the details now, but I assume, standard crystal oscillators?) -- If memory serves, my card has two clocks with configurable multipliers, and cannot drive 3 outputs with incompatible clocks (HDMI, DVI, VGA) -- but with the Display Port edition, one clock can drive both DVI and Display Port. –  BrainSlugs83 Feb 21 '12 at 23:42

I think you underline something important: Dual DVI is NOT equivalent to DVI+ HDMI. The issue is that with dual DVI you can clone and extend the desktop, while with HDMI - the moment you connect the cable the DVI image will disappear. Are you familiar with the Digital Rights Bla Bla ? This is the reason. NVidia are blocking their drivers and prevent them to clone or extend with HDMI plugged in because they somehow assume that this will prevent video pirates (go figure).

So the answer to your question is - unfortunately not. BR

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