I was surprised to find out that although the enhanced docking station for the M6500 (and similar Dell Precision workstation laptops) does seem to accept a Dual-Link DVI cable, the interface between the dock and the laptop doesn’t appear to transmit the data required.

What you end up with is displays like the 3007WFP 30” 2560×1600 display only running at a display resolution of 1280×800.  Fortunately there’s an easy, albeit expensive fix:  buy an adapter and use the Display Port connector on the dock instead.

If you buy a Display Port to Dual Link DVI adapter such as the HP P/N: 492329-001.  (Dell shows this one on their site: http://accessories.us.dell.com/sna/products/cables/productdetail.aspx?c=us&l=en&s=dhs&cs=19&sku=330-5521 ).

DisplayPort to Dual Link DVI Adapter for Dell Optiplex 790 Desktop / Precision M4600 Mobile WorkStations

That adapter has one cable that plugs into a USB port for power and the other to the Display Port.  When connected with that cable you get the full 2560×1600 display resolution.  Important: Make sure you buy the one with the little “tail” that connects to the USB port — if you’re spending under $100 on this you are buying the WRONG PRODUCT — you will not get Dual Link DVI support if it doesn’t have the USB part.