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I have a pair of HP ZR2740w monitors which have a native resolution of 2560x1440. They have DisplayPort and (dual-link) DVI inputs. I just got a Sapphire 1 GB Radeon 5450 with two DVI outputs. I'm running Fedora 16 and have tried the included drivers and the ATI proprietary one from their website.

In all cases, it seems that I can change the resolution of the first monitor up to 2560 pixels, but the second one only to 1280. Why is this? Is there some maximum total resolution limit that I am running into? Does the card not support two dual-link DVI outputs at once? I can't tell from the packaging nor from my experience so far.

If you know of an ATI card that definitely supports dual 2560px outputs with either DVI or DP, and which takes only a single PCI slot and no 6-pin PCIe power, I'd love to hear about it.

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3 Answers 3

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I found a forum thread posted just three days ago that explains:

None of the Radeons come with two dual-DVI ports. If there are two, one is always single-DVI.

This certainly seems to mirror my experience, and is a real let-down from ATI. Oh well, I guess I'm off in search of a DisplayPort card instead.

It is bizarre that they don't just list these facts on the box.

Edit: the solution ended up being the ATI FirePro 2460. It has quad DP outputs and requires no extra power cable. It's also low-profile and fanless.

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On the back of the card, what do the DVI connections look like? There is a difference between a dual-link DVI and a single-link DVI. Or possibly it could be a DVI-D.

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They look like dual-link. And I'm using dual-link cables (that came with the monitors). Single-link DVI should handle at 1920x1080 anyway, or 1600px. One of the ports definitely is DVI-I also, as the card came with one VGA adapter (which I'd try using if my monitors had VGA inputs, but they don't). –  John Zwinck Feb 29 '12 at 16:57

Have you tried arranging one monitor above the other, instead of next-to?

Some cards had a restriction of total desktop size of no more than 4096x4096px, which means two such monitors would not fit horizontally.

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I haven't, though if that's all it can do it may as well be outright broken--the users of this thing mostly don't use vertical monitors. –  John Zwinck Mar 1 '12 at 9:04
    
It's more a matter of arranging monitors on the virtual desktop. They could physically stand next to each other, but the OS will think they are on top of each other. Leads to some confusion on how to move pointer between the two (up/down, not left-right), but it could be a reasonable workaround. I've worked like this on Matrox G450s with two CRTs 2304x1440 years ago, confusing, but still better than just one monitor. –  qdot Mar 1 '12 at 16:22
    
Yeah, that's not a workaround I'd be willing to entertain. Seems moot anyway (see my own answer). –  John Zwinck Mar 1 '12 at 20:04

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