Getting a 30 inch Samsung 305T dual link DVI monitor to work with a Dell XPS Studio 16 (1647) is no easy task. I have googled and googled for an answer, researched HDM-to-DVI adapters, and read Display Port specifications.
I have finally found a solution: A ViDock. It connect using the ExpressCard slot and makes it possible to run a standard PCI Express graphics card, and thus enables the laptop to drive any monitor. I bought the ViDock 4 which can be used for a graphics card with a single power connector. All but the most demanding graphics card can thus be used.
I use an ATI Radeon HD 5770 with the ViDock now. I started out with an ATI Mobility Radeon HD 4350, because it was dead cheap, but it was a bit under powered when YouTube was running in full screen. The full HD resolution of the built-in display is great, but pales in comparison with the WQXGA of the Samsung monitor. Adobe Photoshop Lightroom seems to be built for 2560x1600.
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