Along the top edge of the PCB is a Crossfire connector that can be used to join two of these cards for quad Crossfire or couple an X2 with a regular HD 3870 for three-way Crossfire. Unfortunately, drivers for neither of these configurations are yet available so we'll have to wait a while to see how this performs.
Output configuration is standard fair with two dual-link DVI sockets and TV-out available on the back plate. However, without wishing to steal our own thunder too much, the aforementioned partner card has included four DVI outputs so if quad monitor setups are your thing, variants on the HD 3870 X2 could be the thing to look for.
One strange difference between this card and all similarly large cards is the orientation of the two auxiliary power connectors on the top edge. Just as with the HD 2900 XT, the card requires two six-pin PCI-E power connectors to run properly, and for overclocking you should use one six-pin and one eight-pin connector. The odd thing about the reference connectors, though, is that, rather than facing the connectors upwards, where they're easy to reach when installed in a case, ATI has chosen to mount them perpendicular to the PCB. In our experience this makes it more difficult to attach and remove the power cables, particularly if you're using two of these cards at once.
Fortunately, once again the great unmentionable partner card (ok, it's made by ASUS) shows that ATI's board partners really are willing to tread a different path to that dictated by ATI as they've oriented the power connectors in the conventional way.