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.