I've been following a thread about that over on the SoftTH forums. In a nutshell:
- There are two versions of the ATI 5870 card. The ones you typically see available now, which have 1 Display Port, 2 DVI ports and 1 HDMI port. The other version is a 6 (mini) Display Port card.
- The card being used in the spiffy demos with 6 monitors per card is (obviously) the 6 Display Port version.
- The ones that you typically see now only have 2 DVI channels internally. The result of that is an attempt to use the HDMI port, or the Display Port with a passive Display Port-to-DVI converter, robs a DVI port of a channel, disabling it. Using an active Display Port-to-DVI converter (which are more expensive) can get you up to a third working DVI connection, as I understand it.
************************************************** ****
As one might imagine, this has led to some consternation. Right now, there are not a lot of Display Port monitors on the market, and they are pricey.
Assuming it is possible / feasible, it would be nice to see ATI design a version with 6 DVI channels / connections. Perhaps there will be enough market pressure to lead them in that direction.