I recently ordered a Dell Precision T1600 for someone with an ATI FirePro V4800 in order to have a three monitor setup on their workstation. There was no information at the Dell site about the needs for doing three monitors just that the card could support three. It has one DVI slot and two Display Ports. By default it came with one DP-DVI converter so I added a second to the purchase of the computer.
Once I had the computer in hand and was trying to setup the three displays I was surprised to find it wouldn't work. The card could see all three monitors but it could only display two at a time. After looking up the card at ATI's site and being confused by why they said was necessary to get three monitors to work I had to call and here is the deal.
If you want to have three monitors here is what you need. One monitor plugged into the DVI slot. One monitor plugged into the DP-DVI Passive adapter that comes with the card. One monitor plugged into a DP-DVI Active adapter that you have to buy separately. ATI provides a web page with approved dongles for their cards.
I ordered the Accell DP-DVI Single Link Active adapter and hooked it up today. Everything worked fine. I'm a bit frustrated with Dell that they don't provide better information and offer the needed adapter when buying the computer. When I was searching for a solution to this problem I saw quite a few Dell owners who were having the same issue.