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I have ATI card with VGA, DVI and HDMI. My question is how can I use all three outputs at the same time? I got a HDMI to VGA converter cable, but when all monitors are hooked up, only two monitors are alive at any one time.

Does this phenomenon exist for ALL ATI & nVidia cards? Or is it ATI vards prior to the 5000 series and eyefinity. I have three great monitors and an adequate video card (1 GB) so I am hoping to somehow be able to use 3 monitors and extend my desktop across all three.

Are there any softweare utilities which can probe the Video card and 'patch' the drivers to activate the third port, or is this a physical limitation due to the thrid posrt being a 'peel' from one of the other 2.

Finally, I was tempted to consider a PCI solution in addition to my main PCIe card. The theroy was that thePCI could be used to drive the third display. I had lots of blue screen of death and freezups so I gave that up - drivers are critical in this case if I am not wrong.

Any advice or suggestions would be most welcome.

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2 Answers 2

That card supports (at most) two simultaneous displays. The specs for that chipset tell us it has "Two integrated dual-link DVI display outputs", which means you can plug two monitors into it.

The important thing to recognize here is that a DVI plug supports two signals--one digital, and one analog. But they (in this case) pass the same signal. A DVI-to-VGA adaptor simply ignores the digital signal, and passes the analog signal on to your monitor.

If your card has three plugs, one of which is VGA, it basically just means it has a built-in DVI-to-VGA adaptor, so one of the two display outputs is connected to the VGA and (probably) the HDMI port (HDMI is basically DVI minus the analog signal + optional sound info--which is irrelevant to a video card).

So think of it as a video card with a DVI port, and a HDMI or VGA port.

If you want three monitors, you will need another video card. Your PCI card ought to do the trick, but there can be icky driver issues to deal with. It's always easier to do that with two identical cards (as I do--I have two identical nVidia cards, each with 2 outputs, to drive my 3 monitors).

You also might have better luck with another PCI card that uses different drivers.

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Some cards are capable of three (or more) simultaneous outputs, some are not. This one is not. This is really just down to the specific card, but the vast majority of current generation ATI cards support 3+ outputs if you're using native (or actively converted) DisplayPort connections (this is usually branded as EyeFinity). Nvidia hasn't been as good about supporting it, but there are cards that support it as well in the current generation. Going back a few generations from any non-Matrox manufacturer, it's really hard to find non-workstation cards that support more than two outputs - it's only relatively recently that this has become fairly commonplace.

This is generally a physical limitation of the number of TMDS clocks on the card.

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Hey guys I appreciate your comments. I'm on a very tight budget so I am reluctant to do a whole system upgrade just to enjoy the luxury of a third monitor. Can any one recommend a descent PCI cards (ATI) that can coexist with my PCIe HD4850, or failing that, any nVidia PCI cards that would be happy alongside a Geforce G220 (1GB). Although quite rare (and possibly expensive), I would need to have a minimum of 512MB on the PCI card(s) in order to get good resolution and performance for 3D applications. Unless the rendering can somehow be done on the primary PCIe card - somehow? –  Mystified Jun 17 '11 at 20:31

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