Studio 1640 - Displayport - maximum resolution actually experienced using an external monitor

Hi There Folks,

I have spent a heap of time (days) trying to get the definitive answer to what the maximum resolution is on a Dell Studio 1640 XPS using the ATI Mobility Radeon HD 4670 Displayport adaptor is? I am exceptionally interested in actually experienced maximum resolutions, rather than 'believed information', because Dell itself is giving out conflicting information. So I really would like people who are using an external monitor through the Displayport, with this same laptop configuration to tell me what is the maximum resolution they are/have actually experienced.

The problem seems to stem from the sort of Displayport fitted by Dell into the 1640. It is NOT a Displayport ++ (which should support up to 2560 x 1600) but a plain old Displayport. My understanding is that this restricts the maximum resolution to something less but I cannot get confidence in Dell on this because they keep telling me it will support 2560 x 1600 but there are numerous posts about buying an Dell Ultrasharp U2711 monitor (native resolution 2560 x 1440) and it NOT working. These reports of the U2711 monitor not working on this laptop are normally accompanied by complaints that Dell gave the user incorrect information. Hence why actual experience, using a particular monitor, at a particular resolution will be more convincing.

As background, this is important, as I am involved in Photographic manipulation in Photoshop etc and the highest resolution within my budget is required. I can afford a Dell Ultrasharp U2711 monitor at around AU$799 but forum reports are that this monitor does not work on my laptop configuration.  I have not found a sole report that says an Ultrasharp U2711 monitor does work on the Studio 1640. Yet dell has written an email to me this morning saying to me: "Here’s the monitor that will display the maximum resolution with your computer: Ultrasharp U3011" Which has an even higher resolution (2560 x 1600). So the users on the forums say completely different information to Dell.

Please put me out of my misery by giving me your own actual experiences with external monitors? Thank you.